P1760 NissanP1760 Nissan - Overrun Clutch Solenoid ValveCauses

- Faulty overrun clutch solenoid valve- Overrun clutch solenoid valve harness is open or shorted- Overrun clutch solenoid valve circuit poor electrical connection

When is the code detected?The P1760 code is detected when the Transmission Control Module (TCM) detects an improper voltage drop when it tries to operate the solenoid valve.

Possible symptoms- Engine Light ON (or Service Engine Soon Warning Light)

P1760 Nissan Description

The overrun clutch solenoid valve is activated by the Transmission Control Module (TCM) in response to signals sent from the Park/Neutral Position (PNP) switch, overdrive control switch, vehicle speed and Engine Control Module (ECM).

======================

P1760 TOYOTAP1760 TOYOTA - Linear Solenoid for Line Pressure

Control Circuit Malfunction

Possible causes

- Open or short in shift solenoid valve SLT circuit- Shift solenoid valve SLT- ECM

Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

P1760 TOYOTA Description

The throttle pressure that is applied to the primary regulator valve (which modulates line pressure) causes the shift solenoid valve SLT, under electronic control, to precisely and minutely modulate and generate line pressure according to the accelerator pedal effort, or engine power output detected. This reduces the function of line pressure and provides smooth shifting characteristics. Upon receiving the throttle valve opening angle signal, ECM controls the line pressure by sending a predetermined (*) dutyratio to the solenoid valve, modulating the line pressure, generating throttle pressure.

=================

General Motors OBD II Powertrain Diagnostic Trouble Codes P1700-P1899

Copyright Trouble-Codes.com

Diagnostic Trouble Code numbers are read by plugging a code reader or scan tool into the vehicle diagnostic connector(usually located under the instrument panel near the steering column) that can read vehicle manufacturer enhanced or P1 c

odes (not just generic or P0 codes). The presence of a code will turn on the Check Engine Light. The light will remain on untilthe code has been erased. The code number does not tell you which part has failed. It only indicates a possible fault hasbeen detected in the circuit, system or sensor described. Further testing is usually required to isolate the fault BEFORE

repairs are made.

For vehicle specific diagnostic charts and vehicle specific repair information, refer to a service manual, or get a subscriptionto the GM Tech Info website, or AllDataDIY.

The following is a partial listing of common General Motors specific "P1" enhanced OBD II fault codes:

The following is a partial listing of common General Motors specific "P1" enhanced OBD II fault codes:

GM Trouble Code List P1700-P1899

NOTE: For some code numbers, there may be more than one definition because the same number may be used for differentfaults on different model years or models.

P1700....Malfunction Indicator Lamp requested by trans control module

P1701....Malfunction Indicator Lamp request circuit

P1740....Torque control/management request circuit

P1760....Transmission Control Module supply voltage interrupted

P1780....Park/Neutral Position Switch circuit

P1781....Engine torque signal circuit

P1792....ECM to Transmission Control Module engine coolant signal

P1800....ECM to Transmission Control Module engine coolant signal

P1810....ATF pressure manual valve powition switch malfunction

P1811....Long shift and maximum adaptation limit reached

P1812....TOT condition

P1814....Torque converter clutch (TCC) overstress

P1819....Transmission range switch out of range, possible no start

P1820....Transmission range switch A voltage low

P1822....Transmission range switch B voltage high

P1823....Transmission range switch P voltage low

P1825....Transmission range switch A, B, C & P signals invalid

P1826....Transmission range switch C voltage high

P1835....Kickdown Switch circuit

P1842....1-2 Shift Solenoid circuit low input

P1843....1-2 Shift Solenoid circuit high input

P1845....2-3 Shift Solenoid circuit low input

P1847....2-3Shift Solenoid circuit high input

P1850....Brake Band Aply Solenoid

P1860....Torque Converter Clutch (TCC) PWM Solenoid circuit

P1864....TCC Enable Solenoid circuit

P1868....Transmission Fluid life

P1870....Transmission component slipping

P1873....Oxygen sensor bank 2 sensor 2 cross counts

P1874....Oxygen sensor bank 1 sensor 3 cross counts

P1875....4WD Low Switch circuit electrical

P1886....Transaxle Shift, Timing Solenoid performance

P1887....TCC Release Switch malfunction

P1890....Throttle Position signal input

P1891....Throttle position sensor circuit signal low

P1892....Throttle position sensor circuit signal high

P1895....Engine torque delivered circuit

2001-2003 Rav4 hard/abnormal shifting – P0750, P0753, P0755, P0758, P1760

Owners of a 2001-2004 Rav4 often complain of abnormal shifting, sometimes in conjunction with a check engine light and shift solenoid codes (P0750, P0753, P0755, P0758 and/or P1760). The 2-3 upshift can be particularly harsh, the condition can come and go, and in many cases is incorrectly diagnosed by aftermarket shops unfamiliar with the problem. The problem is so widespread Toyota extended that warranty for this specific issue to 10 years or 150k miles. CARspec had a 2003 Rav4 with this condition last night and we wanted to share our solution to help others that may have the same issue.

In the majority of cases this condition is caused by the Engine Control Module (the main control brain of the car). For reasons unknown, the symptoms start to appear around 80k miles and gradually worsen over time – harsh shifting, poor gear kickdown, and abrupt starts from a stop. The symptoms can come and go, but never disappear entirely. Driving with the symptoms can potentially lead to transmission failure, requiring the replacement of both the module and the transmission.

Toyota offers an updated Engine Control Module for the condition which corrects the condition for most owners. While relatively expensive, the repair is effective in alleviating the harsh shifts and preserving the life of the transmission.

We hope this helps any Rav4 owners or other technicians correctly identify this issue and get it resolved!

P1760 2002 Nissan Altima Sedan

P1760 2002 Nissan Altima Sedan - Overrun Clutch Solenoid Valve

Possible causes

-Faulty overrun clutch solenoid valve -Overrun clutch solenoid valve harness is open or shorted

-Overrun clutch solenoid valve circuit poor electrical connection

What does this mean?

When is the code detected?

The P1760 code is detected when the Transmission Control Module (TCM) detects an improper voltage drop when it tries to operate the solenoid valve.

Possible symptoms

-Engine Light ON (or Service Engine Soon Warning Light)

P1760 2002 Nissan Altima Sedan Description

The overrun clutch solenoid valve is activated by the Transmission Control Module (TCM) in response to signals sent from the Park/Neutral Position (PNP) switch, overdrive control switch, vehicle speed and Engine Control Module (ECM).

Need more help?

Do you need more help with the P1760 2002 Nissan Altima Sedan code? ask a question to our users or search the top hand picked automotive forums for more information

PROBLEM WITH BLOWN FUSE FOR GUAGES

1995 Nissan Altima

Electrical problem1995 Nissan Altima 4 cyl Front Wheel Drive Automatic

I have a 95 Nissan Altima that suddenly started blowing the 10 amp fuse that controls all the guages when the caris placed in Drive only. Everything is fine in all the other gears except Drive. What could it be and where would it be located? Thanks

Toyota U140/U240 Series Diagnostic Information

Jeff Parlee

This transmission has some unique problems that can cause you to scratch your head. Add the lack of information available from the manufacturer and your frustration level can skyrocket. Here are some common problems and suggestions on how to resolve them.

Binding On the 1-2 Shift:

Binding on the 1-2 shift is a common complaint with this transmission. A quick way to determine if you have a valve body/solenoid problem or a faulty ECM is to see if you have reverse with the electrical connector disconnected from the transmission. If you do NOT have reverse, suspect the B2 control valve stuck on or pushed to the apply position by cross leaks or a DSL solenoid stuck open. If the transmission engages into reverse, suspecta faulty ECM .

Here's why. The DSL solenoid, also known as the TCC solenoid, doesn't just come on for lock up. The DSL solenoid is also energized in manual low and is used to inhibit reverse. The DSL solenoid is a normally closed solenoid. When energized, it allows oil pressure to stroke the B2 control valve, apply the B2 clutch in manual low, and block oil to the B2 clutch in reverse. If the DSL solenoid is stuck open in drive, the B2 clutch will apply in 1st as it does in manual low. When the 1-2 shift occurs with the B2 clutch applied, one too many clutches are applied

and the transmission binds up. If the DSL solenoid is stuck open when reverse is selected, the B2 control valve will block oil to the B2 clutch, inhibiting reverse .

The engine and the transmission are controlled by the ECM (Engine Control Module), more commonly known as the PCM (Powertrain Control Module) in these units. It is not uncommon for 2001 – 2003 RAV4 vehicles to have a faulty ECM. Many times the vehicle will have binding or harsh shifts, which are often be accompanied by codes P0750, P0753, P0755, P0758, and P1760. For more information, see Toyota bulletin # TC002-06 with an issue date of March 3, 2006 .

Before you order a new ECM, be aware of the following. Keep in mind that adaptive strategy is used to control this transmission and the learned adapts must be reset to avoid damage to the transmission after a transmission overhaul or valve body replacement. Remember that the reset procedure will reset all of the ECM learned adapts, not just the transmission adapts. The Toyota factory scanner is capable of resetting the ECM adapts. Resetting the adapts should be followed by performing a re-learn procedure. Bring the transaxle to operating temperature. Next, drive the vehicle at light steady throttle through all of the shifts and repeat until the shifts feel normal. You may find that resetting the shift adapts will correct any binding on the shift, without having to replace the ECM. I would highly recommend performing the ECM reset first, before replacing the ECM.

Gear SL1 SL2 SL4 *DSL/TCC

1st On On Of

2nd Of On Of

3rd Of Of Of

3rd TCC on Of Of Of On

4th Of Of On

4th TCC on Of Of On On

Manual 1st On On Of On

2-3 Slip, Flare/Delayed or No Reverse:

The direct clutch sealing rings wear into the ring grooves in the cover and the direct drum is frequently ring grooved. Proper clearance between the sealing ring and the ring land is .003" to .005". Direct drums with damage where the sealing rings ride should be replaced. Do NOTtry to salvage the drum by sanding out the damage .

Another cause of pressure loss to the direct clutch is a missing or incorrectly positioned rubber washer type sealbetween the case and the rear cover.

Slips in Reverse or No Reverse:

In addition to the direct clutch problems, a DSL solenoid that is stuck "on," a B2 control valve that is stuck in the stroked position, or missing or damaged B2 seals between the valve body and case can cause reverse to be delayed, slip or be missing altogether .

Various Shift and Engagement Feel Concerns:

Various shift and engagement feel concerns can be due to accumulator spring mix up. The chart below shows the location, color and dimensions of each accumulator spring in the case .

The C1 accumulator is for neutral to drive engagement feel.

The C3 accumulator is for the 3-4 shift feel.

The B3 accumulator will afect the 4-3 downshift feel.

Bore Spring Location Color Free Length Dia. # Of Coils Wire Dia.

C1 Case side Red 3.555" .727" 14.5 .075"

C3 Outer VB side White 3.645" .738" 14 .117"

C3 Inner VB side Plain .470" .450" 3 .078"

B3 Outer Case side Blue 2.945" .856" 10 .098"

B3 Inner Case side Green 2.370" .625" 12 .085"

As always, information is the key to fixing it right the first time.

How Can I Tell If My AutomaticTransmission Needs an Overhaul?

This tutorial is a primer that'll help you find out if the problem with your Dodge or Jeep's 42RE, 44RE or 46RE

computer controlled transmission is electrical in nature or if the problem is due to internal damage that'll require

an overhaul (without having to drop it and tear it down).

To be a bit more specific, this article will explore the specific symptoms an automatic transmission displays when

its shifting issue/problem is due to an electrical fault (like a bad shift solenoid) or due to an internal/mechanical

failure.

Here are the contents of this article at a quick glance:

42RE, 44RE, 46RE Automatic Transmission Basics.

Two of the Most Common Transmission Failures.

How Can I Tell If It's Just a Solenoid Failure?

How Can I Tell If It's Internal Transmission Damage Requiring an Overhaul?

Transmission with Both Solenoid Failure and Internal Damage.

More Diagnostic/Troubleshooting Tutorials.

Let's get started...

42RE, 44RE, 46RE Automatic Transmission Basics

Vehicles covered by this tutorial use one of the following rear wheel drive (RWD) automatic transmissions: 42RE,

44RE, 46RE. All 3 of these are computer controlled and have an electrically operated valve body to control the

upshifts and downshifts.

All three also provide a self-diagnostic feature as part of their transmission control program. So, if you have a

scan tool... you're able to retrieve transmission diagnostic trouble codes stored in the PCM or TCM (when

something goes wrong with the transmission) to help you troubleshoot the issue/s.

Here are some more specifics:

42RE Automatic Transmission

This is an updated medium-duty A500 with overdrive and electronic control.

Used mainly on the 3.9L V6 equipped RWD vehicles.

Found in:

o 1996-2003 Dodge Dakota 3.9L V6

o 1998-1999 Dodge Durango 3.9L V6

o 1996-2001 Dodge Ram 1500 3.9L

44RE Automatic Transmission

This is an updated heavy-duty A500 with overdrive and electronic control.

Used mainly on the 5.2L equipped Dodge and Jeep vehicles.

Found in:

o 1996-1998 Jeep Grand Cherokee 5.2L V8

o 1998-2000 Dodge Durango 5.2L V8 (4WD (98-99) or 2WD (99-00))

46RE Automatic Transmission

This is an updated A518 with overdrive and electronic control.

Used mainly on 5.9L V8 equipped Dodge and Jeep vehicles.

Found in:

o 1996 Dodge Dakota V8 (Also 98-03 Dakota 5.9L R/T)

o 1996-2002 Dodge Ram 1500/2500/3500 V8

o 1998-2003 Dodge Durango 5.9L V8 (4WD or 2WD)

o 1998 Jeep Grand Cherokee 5.9L V8 (4WD)

o Introduced in the early 1990s, it was used in trucks, vans, and Jeep Grand Cherokees equipped with a 5.9 Liter V-8.

Two of the Most Common Transmission Failures

The most important thing to know, when trying to troubleshoot a transmission problem, is that the 42RE, 44RE, or

46RE automatic transmission usually fails in one of two ways:

1. Transmission is ‘slipping’.

This is the classic symptom of a transmission that's got internal mechanical damage.

NOTE 1: Low transmission fluid level (usually due to a transmission fluid leak) can also cause the transmission to ‘slip’.

NOTE 2: An automatic transmission that's ‘slipping‘ can be best described as having it gointo ‘neutral’ all of a sudden (as you're driving down the road) or when you stick the tranny in Drive or Reverse.

2. Transmission does not shift out of 2nd gear.

This generally happens when the PCM senses an electrical problem and commands the transmission to stay in what is known as ‘Limp In Mode’.

In ‘Limp In Mode’, the automatic transmission will not downshift or upshift at all.

The usual cause of this condition is an electrical issue, like a bad shift solenoid... although some internal mechanical problem/damage can also cause this.

In the next couple of paragraphs, we'll explore the above symptoms more in-depth...

How Can I Tell If It's Just a Solenoid Failure?

The electronically controlled 42RE, 44RE, and 46RE automatic transmissions have several solenoids and sensors that the PCM (or Transmission Control Module = TCM) needs to control the upshifts and downshifts. If any one of these sensors/solenoids fail or the fuse(s) that supplies the solenoids gets blown... the transmission will go into ‘Limp In Mode’.

What makes it pretty easy to tell if the automatic transmission failure is just a solenoid related issue... is the fact that, in 99.9% of the cases, the transmission doesn't ‘slip’.

Here are some very specific symptoms you'll see when a transmission solenoid goes bad:

1. The PCM is also gonna' light up the check engine light (CEL) and store a specific shift solenoid diagnostic trouble code (DTC). All generic OBD II transmission diagnostic troubles codes start with: P07XX (the XX being the last 2 digits of the DTC).

2. You'll see one or several of the following transmission diagnostic trouble codes:

P0700: Transmission Control System Malfunction

P0711: Transmission Fluid Temperature Sensor Circuit Range/Performance

P0712: Transmission Fluid Temperature Sensor Circuit Low Input

P0713: Transmission Fluid Temperature Sensor Circuit High Input

P0720: Output Speed Sensor Circuit Malfunction

P0740: Torque Converter Clutch Circuit Malfunction

P0743: Torque Converter Clutch Circuit Electrical

P0748: Pressure Control Solenoid Electrical

P0753: Shift Solenoid A Electrical

P0783: 3-4 Shift Malfunction

3. You may see one, or several, of the following Manufacturer Specific DTCs:

P1756: Governor Pressure Not Equal To Target At 15-20 PSI

P1757: Governor Pressure Above 3 PSI When Request Is 0 PSI

P1762: Governor Pressure Sensor Offset Improper Voltage

P1763: Governor Pressure Sensor Voltage Too High

P1764: Governor Pressure Sensor Voltage Too Low

P1765: Trans 12 Volt Supply Relay Control Circuit

4. The speedometer does not work and you might have one of the following trouble codes:

P0500: Vehicle Speed Sensor Malfunction

P0501: Vehicle Speed Sensor Range/Performance

P0502: Vehicle Speed Sensor Low Input

P0503: Vehicle Speed Sensor Intermittent/Erratic/High

5. Your 42RE, 44RE, or 46RE automatic transmission will stay in ‘Limp In Mode’, which means it'll stay in 2nd gear no matter what the vehicle speed.

6. As you accelerate your vehicle, it feels very underpowered. This is due to the fact that the transmission is starting out in 2nd gear.

7. At speeds over 35 MPH, the engine feels like it's over-revving. This is also due to the fact that the transmission is staying in 2nd gear and the gear ratio provided by 2nd gear is gonna' keep the engine working pretty hard at any speed above 35 MPH.

Remember, what will tell you that you have a solenoid or internal transmission sensor problem is:

1. You'll have a specific transmission diagnostic trouble code (or a Speed sensor diagnostic trouble code).

2. The automatic transmission does not ‘slip’, no matter how many times you road test your vehicle.

3. The 42RE, 44RE, or 46RE stays in ‘Limp In Mode’.

Let's move on to the next subheading and find out more about the specific symptoms a 42RE, 44RE, or 46RE with internal damage...

How Can I Tell If It's InternalTransmission Damage Requiring an Overhaul?

The biggest give-away, that you're vehicle's automatic transmission is kaput and in need of an overhaul or replacement is that it will ‘slip’.

Here are some more specifics that will let you know if it's time for an overhaul or replacement:

1. The transmission fluid level is OK, but it's very dark to black and has a ‘burned out’ smell.

2. Usually (but not always), the PCM will set a ‘gear ratio error’ transmission diagnostic trouble code. Here are some more specifics:

P0730: Incorrect Gear Ratio

P0731: Gear 1 Incorrect ratio

P0732: Gear 2 Incorrect ratio

P0733: Gear 3 Incorrect ratio

P0734: Gear 4 Incorrect ratio

A gear ratio error trouble code is the PCM's way of letting you know that it knows the transmission is ‘slipping’.

3. As you accelerate your vehicle, the transmission feels like it was thrown into neutral all of a sudden.

4. No 1st gear... specifically, you put the transmission in drive but no matter how much you accelerate the engine, your vehicle does not move.

5. The transmission shifts into 1st gear a few seconds after you've come to a complete stop causing a very noticeable jolt (this jolt is more pronounced the faster you've been traveling and the quicker you come to a complete stop). The normal behavior is the transmission shifting into 1st gear before you come to a complete stop.

6. No Reverse gear, although the transmission seems to work fine in Drive.

7. When you remove the transmission oil pan, you find dark sediment. This sediment is the friction material that has fallen off the friction discs (which are located inside the transmission).

8. You may find metal shavings in the fluid pan mixed in with the friction material sediment on the transmission's oil pan.

Removing the transmission oil pan to see if you have metal shavings and/or friction material sediment on the pan is what will give you the definite proof that you have internal transmission damage (and in need of a transmission overhaul).

Transmission with BothSolenoid Failure and Internal Damage

I wanted to make you aware that it's possible for your 42RE, 44RE, or 46RE equipped vehicle to have a failed shift solenoid and internal transmission damage. This is especially true in cases where the internal damage is in the components that create 3rd or 4th gear. What makes the ‘slippage’ (this damage creates) unnoticeable is the simple fact that the transmission doesn't upshift into its higher gears because it's in ‘Limp In Mode’.

From personal experience... I have seen cases where the vehicle had a solenoid or transmission sensorissue, along with a specific transmission trouble code and a bad shift solenoid or bad transmission sensor... and yet once the failed solenoid/sensor was replaced and the transmission started shifting again... it started to slip in 3rd or 4th gear.

There are a few ways to find out if this is the case in your particular case (like checking for sediment andmetal shavings in the pan as you're replacing the shift solenoids)... but ultimately it all boils down to replacing the defective solenoid/sensor and road testing the vehicle.

In Conclusion

Hopefully this article has given you the info you need to be able to say that the issue affecting your automatic transmission is an electrical issue or an internal issue (that requires an overhaul).

If you'd like to share your particular experience with the rest of us (which I'll include in an update to this article), you can use the contact form below:

Symptom:

P1765-TRANS 12 VOLT SUPPLY RELAY CTRL CIRCUIT

When Monitored and Set Condition:

P1765-TRANS 12 VOLT SUPPLY RELAY CTRL CIRCUIT

When Monitored: Continuously with the key on.

Set Condition: This code will set if the voltage detected on the Transmission Relay

Control circuit at the PCM is different than the expected voltage for 3 seconds.

POSSIBLE CAUSES

TRANSMISSION CONTROL RELAY

INTERMITTENT TRANS 12 VOLT SUPPLY RELAY

GENERATOR SOURCE CIRCUIT SHORTED TO GROUND

TRANSMISSION RELAY CONTROL CIRCUIT SHORTED TO GROUND

GENERATOR SOURCE CIRCUIT OPEN

TRANSMISSION RELAY CONTROL CIRCUIT OPEN

PCM

TEST ACTION APPLICABILITY

1 Turn the ignition on.

With the DRB, read DTCs.

Is the Specific Good Trip Counter for P-1765 displayed and equal to 0?

All

Yes ® Go To 2

No ® Go To 9

2 Turn the ignition on.

With the DRB, actuate the Transmission Control Relay.

Is the Transmission Control Relay clicking?

All

Yes ® Go To 9

No ® Go To 3

3 Turn the ignition off.

Remove the Transmission Control Relay from the PDC.

Check connectors - Clean/repair as necessary.

Install a substitute relay in place of the Transmission Control Relay.

Turn the ignition on.

With the DRB, erase trouble codes.

Start the engine.

With the DRB, read DTCs.

Does the DRB display 9Trans 12 Volt Supply Relay Ctrl Circuit9?

All

Yes ® Go To 4

No ® Replace the Transmission Control Relay.

Perform the Transmission DTC Verification test.

338

TEST ACTION APPLICABILITY

4 Turn the ignition off.

Remove the Transmission Control Relay from the PDC.

Disconnect the PCM harness connectors.

Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the generator source circuit in the

Transmission Control Relay connector.

Is the resistance below 5.0 ohms?

All

Yes ® Repair the generator source circuit for a short to ground.

Perform the Transmission DTC Verification test.

No ® Go To 5

5 Turn the ignition off.

Remove the Transmission Control Relay from the PDC.

Disconnect the PCM C2 harness connector.

Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the transmission control relay control

circuit in the Transmission Control Relay connector.

Is the resistance below 5.0 ohms?

All

Yes ® Repair the transmission control relay control circuit for a short to

ground.

Perform the Transmission DTC Verification test.

No ® Go To 6

6 Turn the ignition off.

Remove the Transmission Control Relay from the PDC.

Check connectors - Clean/repair as necessary.

Turn the ignition on.

With the DRB, actuate the Generator Field.

Measure the voltage of the generator source circuit in the Transmission Control

Relay connector.

Is the voltage above 10.0 volts?

All

Yes ® Go To 7

No ® Repair the generator source circuit for an open.

Perform the Transmission DTC Verification test.

7 Turn the ignition off.

Remove the Transmission Control Relay from the PDC.

Disconnect the PCM C2 harness connector.

Check connectors - Clean/repair as necessary.

Measure the resistance of the transmission control relay control circuit between the

Transmission Control Relay connector and the PCM C2 harness connector.

Is the resistance below 5.0 ohms?

All

Yes ® Go To 8

No ® Repair the transmission control relay control circuit for an open.

Perform the Transmission DTC Verification test.

8 If there are no possible causes remaining, view repair. All

Repair

Replace the Powertrain Control Module.

Perform the Transmission DTC Verification test.

339

TRANSMISSION

P1765-TRANS 12 VOLT SUPPLY RELAY CTRL CIRCUIT - Continued

DTC is ''Diagnostic Trouble Code''; this is your P1765

DRB is the Chrysler Diagnostic

Scanner that is necessary for many diagnostic functions.

Here is the PCM location on the

Firewall

1 - POWERTRAIN CONTROL MODULE (PCM)

2 - WIPER MOTOR

3 - PCM MOUNTING BOLTS (3)

4 -XXXXXCONNECTORS (3)

============================

How Can I Tell If My AutomaticTransmission Needs an Overhaul?

This tutorial is a primer that'll help you find out if the problem with your Dodge or Jeep's 42RE, 44RE or 46RE

computer controlled transmission is electrical in nature or if the problem is due to internal damage that'll require

an overhaul (without having to drop it and tear it down).

To be a bit more specific, this article will explore the specific symptoms an automatic transmission displays when

its shifting issue/problem is due to an electrical fault (like a bad shift solenoid) or due to an internal/mechanical

failure.

Here are the contents of this article at a quick glance:

Let's get started...

42RE, 44RE, 46RE Automatic Transmission Basics

Vehicles covered by this tutorial use one of the following rear wheel drive (RWD) automatic transmissions: 42RE,

44RE, 46RE. All 3 of these are computer controlled and have an electrically operated valve body to control the

upshifts and downshifts.

All three also provide a self-diagnostic feature as part of their transmission control program. So, if you have a

scan tool... you're able to retrieve transmission diagnostic trouble codes stored in the PCM or TCM (when

something goes wrong with the transmission) to help you troubleshoot the issue/s.

Here are some more specifics:

42RE Automatic Transmission

This is an updated medium-duty A500 with overdrive and electronic control.

Used mainly on the 3.9L V6 equipped RWD vehicles.

Found in:

o 1996-2003 Dodge Dakota 3.9L V6

o 1998-1999 Dodge Durango 3.9L V6

o 1996-2001 Dodge Ram 1500 3.9L

44RE Automatic Transmission

This is an updated heavy-duty A500 with overdrive and electronic control.

Used mainly on the 5.2L equipped Dodge and Jeep vehicles.

Found in:

o 1996-1998 Jeep Grand Cherokee 5.2L V8

o 1998-2000 Dodge Durango 5.2L V8 (4WD (98-99) or 2WD (99-00))

46RE Automatic Transmission

This is an updated A518 with overdrive and electronic control.

Used mainly on 5.9L V8 equipped Dodge and Jeep vehicles.

Found in:

o 1996 Dodge Dakota V8 (Also 98-03 Dakota 5.9L R/T)

o 1996-2002 Dodge Ram 1500/2500/3500 V8

o 1998-2003 Dodge Durango 5.9L V8 (4WD or 2WD)

o 1998 Jeep Grand Cherokee 5.9L V8 (4WD)

o Introduced in the early 1990s, it was used in trucks, vans, and Jeep Grand Cherokees equipped with a 5.9 Liter V-8.

Two of the Most Common Transmission Failures

The most important thing to know, when trying to troubleshoot a transmission problem, is that the 42RE, 44RE, or

46RE automatic transmission usually fails in one of two ways:

1. Transmission is ‘slipping’.

This is the classic symptom of a transmission that's got internal mechanical damage.

NOTE 1: Low transmission fluid level (usually due to a transmission fluid leak) can also cause the transmission to ‘slip’.

NOTE 2: An automatic transmission that's ‘slipping‘ can be best described as having it gointo ‘neutral’ all of a sudden (as you're driving down the road) or when you stick the tranny in Drive or Reverse.

2. Transmission does not shift out of 2nd gear.

This generally happens when the PCM senses an electrical problem and commands the transmission to stay in what is known as ‘Limp In Mode’.

In ‘Limp In Mode’, the automatic transmission will not downshift or upshift at all.

The usual cause of this condition is an electrical issue, like a bad shift solenoid... although some internal mechanical problem/damage can also cause this.

In the next couple of paragraphs, we'll explore the above symptoms more in-depth...

How Can I Tell If It's Just a Solenoid Failure?

The electronically controlled 42RE, 44RE, and 46RE automatic transmissions have several solenoids and sensors that the PCM (or Transmission Control Module = TCM) needs to control the upshifts and downshifts. If any one of these sensors/solenoids fail or the fuse(s) that supplies the solenoids gets blown... the transmission will go into ‘Limp In Mode’.

What makes it pretty easy to tell if the automatic transmission failure is just a solenoid related issue... is the fact that, in 99.9% of the cases, the transmission doesn't ‘slip’.

Here are some very specific symptoms you'll see when a transmission solenoid goes bad:

1. The PCM is also gonna' light up the check engine light (CEL) and store a specific shift solenoid diagnostic trouble code (DTC). All generic OBD II transmission diagnostic troubles codes start with: P07XX (the XX being the last 2 digits of the DTC).

2. You'll see one or several of the following transmission diagnostic trouble codes:

P0700: Transmission Control System Malfunction

P0711: Transmission Fluid Temperature Sensor Circuit Range/Performance

P0712: Transmission Fluid Temperature Sensor Circuit Low Input

P0713: Transmission Fluid Temperature Sensor Circuit High Input

P0720: Output Speed Sensor Circuit Malfunction

P0740: Torque Converter Clutch Circuit Malfunction

P0743: Torque Converter Clutch Circuit Electrical

P0748: Pressure Control Solenoid Electrical

P0753: Shift Solenoid A Electrical

P0783: 3-4 Shift Malfunction

3. You may see one, or several, of the following Manufacturer Specific DTCs:

P1756: Governor Pressure Not Equal To Target At 15-20 PSI

P1757: Governor Pressure Above 3 PSI When Request Is 0 PSI

P1762: Governor Pressure Sensor Offset Improper Voltage

P1763: Governor Pressure Sensor Voltage Too High

P1764: Governor Pressure Sensor Voltage Too Low

P1765: Trans 12 Volt Supply Relay Control Circuit

4. The speedometer does not work and you might have one of the following trouble codes:

P0500: Vehicle Speed Sensor Malfunction

P0501: Vehicle Speed Sensor Range/Performance

P0502: Vehicle Speed Sensor Low Input

P0503: Vehicle Speed Sensor Intermittent/Erratic/High

5. Your 42RE, 44RE, or 46RE automatic transmission will stay in ‘Limp In Mode’, which means it'll stay in 2nd gear no matter what the vehicle speed.

6. As you accelerate your vehicle, it feels very underpowered. This is due to the fact that the transmission is starting out in 2nd gear.

7. At speeds over 35 MPH, the engine feels like it's over-revving. This is also due to the fact that the transmission is staying in 2nd gear and the gear ratio provided by 2nd gear is gonna' keep the engine working pretty hard at any speed above 35 MPH.

Remember, what will tell you that you have a solenoid or internal transmission sensor problem is:

1. You'll have a specific transmission diagnostic trouble code (or a Speed sensor diagnostic trouble code).

2. The automatic transmission does not ‘slip’, no matter how many times you road test your vehicle.

3. The 42RE, 44RE, or 46RE stays in ‘Limp In Mode’.

Let's move on to the next subheading and find out more about the specific symptoms a 42RE, 44RE, or 46RE with internal damage...

How Can I Tell If It's InternalTransmission Damage Requiring an Overhaul?

The biggest give-away, that you're vehicle's automatic transmission is kaput and in need of an overhaul or replacement is that it will ‘slip’.

Here are some more specifics that will let you know if it's time for an overhaul or replacement:

1. The transmission fluid level is OK, but it's very dark to black and has a ‘burned out’ smell.

2. Usually (but not always), the PCM will set a ‘gear ratio error’ transmission diagnostic trouble code. Here are some more specifics:

P0730: Incorrect Gear Ratio

P0731: Gear 1 Incorrect ratio

P0732: Gear 2 Incorrect ratio

P0733: Gear 3 Incorrect ratio

P0734: Gear 4 Incorrect ratio

A gear ratio error trouble code is the PCM's way of letting you know that it knows the transmission is ‘slipping’.

3. As you accelerate your vehicle, the transmission feels like it was thrown into neutral all of a sudden.

4. No 1st gear... specifically, you put the transmission in drive but no matter how much you accelerate the engine, your vehicle does not move.

5. The transmission shifts into 1st gear a few seconds after you've come to a complete stop causing a very noticeable jolt (this jolt is more pronounced the faster you've been traveling and the quicker you come to a complete stop). The normal behavior is the transmission shifting into 1st gear before you come to a complete stop.

6. No Reverse gear, although the transmission seems to work fine in Drive.

7. When you remove the transmission oil pan, you find dark sediment. This sediment is the friction material that has fallen off the friction discs (which are located inside the transmission).

8. You may find metal shavings in the fluid pan mixed in with the friction material sediment on the transmission's oil pan.

Removing the transmission oil pan to see if you have metal shavings and/or friction material sediment on the pan is what will give you the definite proof that you have internal transmission damage (and in need of a transmission overhaul).

Transmission with BothSolenoid Failure and Internal Damage

I wanted to make you aware that it's possible for your 42RE, 44RE, or 46RE equipped vehicle to have a failed shift solenoid and internal transmission damage. This is especially true in cases where the internal damage is in the components that create 3rd or 4th gear. What makes the ‘slippage’ (this damage creates) unnoticeable is the simple fact that the transmission doesn't upshift into its higher gears because it's in ‘Limp In Mode’.

From personal experience... I have seen cases where the vehicle had a solenoid or transmission sensorissue, along with a specific transmission trouble code and a bad shift solenoid or bad transmission sensor... and yet once the failed solenoid/sensor was replaced and the transmission started shifting again... it started to slip in 3rd or 4th gear.

There are a few ways to find out if this is the case in your particular case (like checking for sediment andmetal shavings in the pan as you're replacing the shift solenoids)... but ultimately it all boils down to replacing the defective solenoid/sensor and road testing the vehicle.

In Conclusion

Hopefully this article has given you the info you need to be able to say that the issue affecting your automatic transmission is an electrical issue or an internal issue (that requires an overhaul).

If you'd like to share your particular experience with the rest of us (which I'll include in an update to this article), you can use the contact form below:

1999 Dodge Durango: 5.9l 4X4..check engine light..errorcodes..12 VOLT

Customer Question

I have a 1999 Dodge Durango 5.9l 4X4 The check engine light turned on so i went to auto zone and they scanned it.it showed error codes P1765-TRANS 12 VOLT SUPPLY RELAY CTRL CIRCUITP0753-TRANS 3-4 SHIFT SOL/TRANS RELAY CIRCUITS

I replaced the relay and cleared the codes, then a few days later the light came back with the same codes.And now i can tell the transmision isn't shifting properly.It seems to not be shifting into O/D on the highwayand also seems to start up in 2 or 3 gear from a stand still.

Sounds like the pcm is going to be bad or the center connector at the pcm is not making contact. The transmission is in limp in mode. Ground the Pink wire at pin 30 in the center Powertrain Control Module connector when plugged in. If the transmission shifts OK now, check the terminal at pin 30. If OK,

replace the PCM. The pcm grounds this circuit to activate the relay you changed.

--------------------

Kia Spectra: 2003 Kia Spectra base w/ automatictransmission

o Customer Question

o 2003 Kia Spectra base w/ automatic transmission -

When in drive, I only have second gear. I can manually shift down into 1st, but when it's in drive I only

have 2nd. No overdrive light when I push the button. OBD2 codes P1693 and P1765. This car has given

me problems with loose connectors (throttle position sensor, etc.) in the past. What's my least expensive

option?

o Ok, with both of these codes, the possible causes are the same - either a short to ground, open in

circuit or faulty ECM/TCM.

check for loose wiring at the ECM/TCM connectors, check for chafing or breaking of the wiring harness

where it goes thru the firewall. If all is ok, then there is only one other option - replace the ECM/TCM

P1693

o Function

o The Malfunction lndicator Lamp (MIL), which is located in the instrument cluster, comes on to

notify the driver that there may be a problem with the vehicle and that service is needed. Lmmediately after

the ignition switch turnson, the malfunction indicator lamp is lit to indicate that the MIL operates normally

and goes off after starting.

o DTC Description

o

o ECM sets DTC P1693 if the ECM detects that the MIL control circuit is open or shorted ground or

bettery..

o

o DTC Detecting Condition

o

o o Detecting Condition o Possible Cause

o Item

o

o DTC Strategy

o ● Signal check o ● Contact resistance in

connectors

● Open or short in circuit

● TCM/ECM

o

o Enable Conditions

o

o

o Threshold Value

o ● High / low check

o

o Diagnostic Time

o ● 20 sec

o

o MIL On Condition

o ● 2 Driving Cycles

o

o

P1765

o

o

o Function

o

o

o

o ECM(Engine Control Module) uses torque reduction signal from TCM to reduce the shift shock by

controlling ignition timing. If duty ratio is approx. 9%, ECM advances ignition timing to approx. 20

degrees and If duty ratio is approx. 90%, ECM retards ignition timing to approx. 20 degrees.

o

o

o

o

o DTC Description

o

o

o

o This DTC is set when the value is out of threshold value.

o

o

o

o

o DTC Detecting Condition

o

o

o

o

o Item

o Detecting Conditiono Possible Cause

o

o DTC

Strategy

o ● Signal check

o ● Contact resistance in

connectors

● Open or short in circuit

● TCM/ECM

o

o Enable

Conditions

o ● Torque reduction status /

clutch status

o

o Threshold

Value

o ● Duty cycle from TCM <

5% or >95%

o

o Diagnostic

Time

o ● Continuous

o

o MIL On

Condition

o ● 2 Driving Cycles

o

o

o

o

o

o

o

o

o

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SERVICE OR EXCELLENT SERVICE to complete transaction or ask for more help by clicking REPLY

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these, please reply first so that I can further help you

o

-------------------

o P1720 Nissan

o P1720 Nissan - Vehicle Speed Meter Circuit Malfunction

o Possible causes

o - VDC/TCS/ABS to ECM circuit harness is open or shorted

- TCM to ECM circuit harness is open or shorted

- VDC/TCS/ABS to ECM circuit connectors

- TCM to ECM circuit connectors

- Faulty revolution sensor

o What does this mean?

o When is the code detected?

o Malfunction is detected when ECM detects a difference between two vehicle speed sensor signals is

out of the specified range.

o Possible symptoms

o - Engine Light ON (or Service Engine Soon Warning Light)

o P1720 Nissan Description

o The Engine Control Module (ECM) receives two vehicle speed sensor signals via the Control Area

Network (CAN) communication line. One is sent from Vehicle Dynamic Control (VDC) / Traction Control

System (TCS) / Anti-Lock Brake System (ABS) control unit, and the other is from Transmission Control

Module (TCM). ECM uses these two signals for engine control.

o Nissan Altima 2007-2012 Service Manual: P1720 VSS

o Description

o ECM receives two vehicle speed signals via the CAN communication line. One is sent from

“ABS actuator and electric unit (control unit)” via the combination meter, and the other is from

TCM (Transmission control module).

o ECM uses these signals for engine control.

o DTC Logic

o DTC DETECTION LOGIC

o NOTE: • If DTC P1720 is displayed with DTC UXXXX first perform the trouble diagnosis for

DTC UXXXX. Refer to EC-1179, "DTC Logic".

o • If DTC P1720 is displayed with DTC P0607, first perform the trouble diagnosis for DTC

P0607. Refer to EC-1378, "DTC Logic".

o

o

o DTC CONFIRMATION PROCEDURE

o 1.PRECONDITIONING

o If DTC Confirmation Procedure has been previously conducted, always perform the following

before conducting the next test.

o 1. Turn ignition switch OFF and wait at least 10 seconds.

o 2. Turn ignition switch ON.

o 3. Turn ignition switch OFF and wait at least 10 seconds.

o >> GO TO 2.

o 2.PERFORM DTC CONFIRMATION PROCEDURE

o 1. Start engine.

o 2. Drive vehicle at a speed of 20 km/h (12 MPH) or more for at least 5 seconds without depressing

the brake pedal.

o 3. Check 1st trip DTC.

o Is 1st trip DTC detected? YES >> Go to EC-1426, "Diagnosis Procedure".

o NO >> INSPECTION END

o Diagnosis Procedure

o 1.CHECK DTC WITH TCM

o Check DTC with TCM. Refer to TM-221, "DTC Index".

o Is the inspection result normal? YES >> GO TO 2.

o NO >> Perform trouble shooting relevant to DTC indicated.

o 2.CHECK DTC WITH “ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT)”

o Refer to BRC-223, "DTC No. Index".

o Is the inspection result normal? YES >> GO TO 3.

o NO >> perform trouble shooting relevant to DTC indicated.

o 3.CHECK COMBINATION METER FUNCTION

o Refer to MWI-95, "DTC Index".

o Transmission Shift And Drivability Enhancements DTCs P0711, P0887, P1720, P1D98, P215C,

U0401 – 2014 Jeep Cherokee

o SUBJECT:

o Flash: Transmission Shift And Drivability Enhancements

o

o OVERVIEW:

o This bulletin involves reprogramming the Transmission Control Module (TCM) with the latest

available software followed by a drive validation.

o

o MODELS:

o 2014 (KL) Jeep Cherokee (International only)

o NOTE: This bulletin applies to vehicles equipped with a 2.0L Turbo Diesel engine (Sales Code

EBT) and a 948TE 9-speed automatic transmission (Sales Code DFH or DFJ).

o

o SYMPTOM/CONDITION:

o The following software enhancement, for the 948TE 9-speed transmission, is being released to

improve diagnostics for the following Diagnostic Trouble Codes (DTCs):

o P0711 – Transmission Fluid Temperature Sensor A Circuit Range-Performance

o P0887 – TCM Power Control Circuit High

o P1720 – Output Speed Sensor-Wheel Speed Rationality

o P1D98 – Incorrect Gear Ratio Clutch B or D Defective

o P215C – Output Shaft Speed Wheel Speed Correlation

o U0401 – Implausible Data Received From ECM-PCM

o The software also enables DTC P07A7 – Transmission Friction Element C Stuck On to set in the

case of a dislodged C-clutch snap-ring.

o

o DIAGNOSIS:

o Using a Scan Tool (wiTECH) with the appropriate Diagnostic Procedures available in

TechCONNECT, verify all engine systems are functioning as designed. If DTCs or symptom conditions,

other than the ones listed above are present, record the issues on the repair order and repair as necessary

before proceeding further with this bulletin.

o If the customer describes the symptom/condition listed above or if the technician finds the DTC,

perform the Repair Procedure.

o

o REPAIR PROCEDURE:

o CAUTION: The Engine Control Module (ECM) must be updated to the latest available software at

the conclusion of this repair procedure. Refer to all applicable published service bulletins for detailed

repair procedures and labor times regarding updating the ECM software.

o NOTE: Install a battery charger to ensure battery voltage does not drop below 13.2 volts. Do not

allow the charging voltage to climb above 13.5 volts during the flash process.

o NOTE: If this flash process is interrupted/aborted, the flash should be restarted.

o 1. Reprogram the TCM with the latest available software. Detailed instructions for flashing control

modules using the wiTECH Diagnostic Application are available by selecting the “HELP” tab on the upper

portion of the wiTECH window, then “HELP CONTENTS.” This will open the Welcome to wiTECH Help

screen where help topics can be selected.

o 2. Using wiTECH, perform the TCM “VIN Verification” routine located in the TCM “Misc

Functions” menu and follow the on-screen prompts.

o 3. Using wiTECH, perform a “PROXI Configuration Alignment” routine located in the “Vehicle

Preparations” tab on the main vehicle view screen.

o 4. Clear any DTCs that may have been set in any modules due to reprogramming. The wiTECH

application will automatically present all DTCs after the flash and allow the them to be cleared.

o 5. Turn the ignition off, disconnect the wiTECH, open and close the door and let vehicle sit for 1

minute.NOTE: Before proceeding to the next step, verify the ECM is programmed with the latest available

software. Refer to all applicable published service bulletins for detailed repair procedures and labor times

regarding updating the ECM software.

o NOTE: Verify that the Clutch Filling Counters and Fast Filling Counters were not reset to 0 (zero)

after flashing using Wi-Tech. If they have reset then 9 Speed Adaptation Drive Learn will have to be

performed at the conclusion of this service bulletin.

o

o 6. Perform a Transmission Drive Verification Test by performing the following steps:

o a. Start the vehicle and allow the coolant temperature to reach between 35°C and 105°C (95°F and

221°F).

o b. Allow the transmission temperature to reach between 50°C and 115°C (122°F and 239°F).

o c. Ensure the vehicle is below an attitude of 2.4 km (8000 ft.).

o d. With the vehicle located in a suitable area and traveling in a straight line, bring the vehicle to a

minimum of 48 kph (30 mph) (5th gear) and perform a 0 throttle coasting deceleration until the

transmission downshifts from 5th gear to 4th gear.

o e. Repeat this coasting downshift 10 times.

o 7. Did the TCM set DTC P07A7 as active?

o Yes>>> Refer to all current, normal diagnostics published in DealerCONNECT/TechCONNECT

regarding the DTC P07A7 and repair as necessary following normal warranty repair guidelines.

o No>>> If all of the Clutch Filling Counters and Fast Filling Counters were reset to 0 (zero) after

flashing, the 9 Speed Adaptation Drive Learn must be performed. Refer to all applicable published service

bulletins regarding the 9 Speed Adaptation Drive Learn for detailed repair procedures and labor times. If

they have not reset, then no further action is required.

o

o P1720 VSS

Description

ECM receives two vehicle speed signals via the CAN communication line. One is sent from "ABS actuator

and electric unit (control unit)" via the combination meter, and the other is from TCM (Transmission

control module). ECM uses these signals for engine control.

DTC Logic

DTC DETECTION LOGIC

NOTE:

o If DTC P1720 is displayed with DTC UXXXX first perform the trouble diagnosis for DTC

UXXXX. Refer to See: U Code Charts\U0101.

o If DTC P1720 is displayed with DTC P0607, first perform the trouble diagnosis for DTC P0607.

Refer to See: P0607.

o

o

DTC CONFIRMATION PROCEDURE

1.PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always perform the following before

conducting the next test.

o Turn ignition switch OFF and wait at least 10 seconds.

o Turn ignition switch ON.

o Turn ignition switch OFF and wait at least 10 seconds. >> GO TO 2.

o 2.PERFORM DTC CONFIRMATION PROCEDURE

o Start engine.

o Drive vehicle at a speed of 20 km/h (12 MPH) or more for at least 5 seconds without depressing the

brake pedal.

o Check 1st trip DTC. Is 1st trip DTC detected?

o YES >> Go to Diagnosis Procedure.

NO >> Inspection END

Diagnosis Procedure

1.CHECK DTC WITH TCM

Check DTC with TCM. Refer to See: Testing and Inspection.

Is the Inspection result normal?

YES >> GO TO 2.

NO >> Perform trouble shooting relevant to DTC indicated.

2.CHECK DTC WITH "ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT)"

Refer to See: Testing and Inspection.

Is the Inspection result normal?

YES >> GO TO 3.

NO >> perform trouble shooting relevant to DTC indicated.

3.CHECK COMBINATION METER FUNCTION

Refer to See: Testing and Inspection.

>> Inspection END

-=======================

P1794 OBD Trouble Code

P1794 - Kia

Type Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled

DescriptionSupply voltage

Cause Wiring, fuse, battery

DTC P1794:16 [ADVANCED KEYLESS ENTRY AND PUSHBUTTON START SYSTEM]

id09021c933100

DESCRIPTIONLow voltage in power supply circuit (+B2)

DETECTION CONDITION• Keyless control module power supply circuit (+B2) voltage is less than 8.5 V for 5 s.

POSSIBLE CAUSE

• Charging system malfunction

― PCM DTC is stored

• Battery malfunction

• Generator malfunction

• Keyless control module connector or terminals malfunction

• Open circuit or short to ground in keyless control module power supply circuit

― Short to ground in wiring harness between battery positive terminal and keyless control module terminal 1F

― ENG+B 10 A fuse malfunction

― Open circuit in wiring harness between battery positive terminal and keyless control module terminal 1F

• Keyless control module malfunction

DESCRIPTIONLow voltage in power supply circuit (+B2)

Diagnostic Procedure

StepInspectionAction

1

CONFIRM PCM DTC

• Perform the PCM DTC inspection using the M-MDS.

(See ON-BOARD DIAGNOSTIC TEST [MZR 1.5, MZR 1.6].)

(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0, MZR 2.5].)

(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0 DISI i-stop].)

(See ON-BOARD DIAGNOSTIC TEST [MZR 2.3 DISI Turbo].)

(See ON-BOARD DIAGNOSTIC TEST [MZR-CD 2.2].)

(See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0].)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [MZR 1.5, MZR 1.6].)

(See DTC TABLE [MZR 2.0, MZR 2.5].)

(See DTC TABLE [MZR 2.0 DISI i-stop].)

(See DTC TABLE [MZR 2.3 DISI Turbo].)

(See DTC TABLE [MZR-CD 2.2].)

(See DTC TABLE [SKYACTIV-G 2.0].)

NoGo to the next step.

2INSPECT BATTERY

• Inspect the battery.

(See BATTERY INSPECTION [MZR 1.5, MZR 1.6].)

(See BATTERY INSPECTION [MZR 2.0, MZR 2.5].)

(See BATTERY INSPECTION [MZR 2.0 DISI i-stop].)

(See BATTERY INSPECTION [MZR 2.3 DISI Turbo].)

(See BATTERY INSPECTION [MZR-CD 2.2].)

(See BATTERY INSPECTION [SKYACTIV-G 2.0].)

• Is there any malfunction?

YesRecharge or replace the battery, then go to Step 6.

(See BATTERY RECHARGING [MZR 1.5, MZR 1.6].)

(See BATTERY RECHARGING [MZR 2.0, MZR 2.5].)

(See BATTERY RECHARGING [MZR 2.0 DISI i-stop].)

(See BATTERY RECHARGING [MZR 2.3 DISI Turbo].)

(See BATTERY RECHARGING [MZR-CD 2.2].)

(See BATTERY RECHARGING [SKYACTIV-G 2.0].)

(See BATTERY REMOVAL/INSTALLATION [MZR 1.5, MZR 1.6].)

(See BATTERY REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)

StepInspectionAction

(See BATTERY REMOVAL/INSTALLATION [MZR 2.0 DISI i-stop].)

(See BATTERY REMOVAL/INSTALLATION [MZR 2.3 DISI Turbo].)

(See BATTERY REMOVAL/INSTALLATION [MZR-CD 2.2].)

(See BATTERY REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

NoGo to the next step.

3

INSPECT GENERATOR

• Inspect the generator.

(See GENERATOR INSPECTION [MZR 1.5, MZR 1.6].)

(See GENERATOR INSPECTION [MZR 2.0, MZR 2.5].)

(See GENERATOR INSPECTION [MZR 2.0 DISI i-stop].)

(See GENERATOR INSPECTION [MZR 2.3 DISI Turbo].)

(See GENERATOR INSPECTION [MZR-CD 2.2].)

(See GENERATOR INSPECTION [SKYACTIV-G 2.0].)

• Is there any malfunction?

Yes

Replace the generator, then go to Step 6.

(See GENERATOR REMOVAL/INSTALLATION [MZR 1.5, MZR 1.6].)

(See GENERATOR REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)

(See GENERATOR REMOVAL/INSTALLATION [MZR 2.0 DISI i-stop].)

(See GENERATOR REMOVAL/INSTALLATION [MZR 2.3 DISI Turbo].)

(See GENERATOR REMOVAL/INSTALLATION [MZR-CD 2.2].)

(See GENERATOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

NoGo to the next step.

4

INSPECT KEYLESS CONTROL MODULE CONNECTOR AND TERMINALS

• Switch the ignition to off.

• Disconnect the negative battery cable.

• Disconnect the keyless control module connector.

• Inspect the connector and terminals (corrosion, damage, pin disconnection).

• Is there any malfunction?

YesRepair or replace the connector or terminals, then go to Step 6.

NoGo to the next step.

5INSPECT POWER SUPPLY CIRCUIT (+B2) FOR OPEN CIRCUIT OR SHORT TO GROUND

• Keyless control module connector is disconnected.

• Reconnect the negative battery cable.

(See BATTERY REMOVAL/INSTALLATION [MZR 1.5, MZR 1.6].)

(See BATTERY REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)

YesGo to the next step.

NoInspect the ENG+B 10 A fuse.

• If the fuse is melt:

― Repair or replace the wiring harness for a possible short to ground.

― Replace the fuse.

• If the fuse is deterioration:

StepInspectionAction

(See BATTERY REMOVAL/INSTALLATION [MZR 2.0 DISI i-stop].)

(See BATTERY REMOVAL/INSTALLATION [MZR 2.3 DISI Turbo].)

(See BATTERY REMOVAL/INSTALLATION [MZR-CD 2.2].)

(See BATTERY REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

• Measure the voltage at the following terminal (wiring harness-side):

― Keyless control module terminal 1F

• Is the voltage B+?

― Replace the fuse.

• If the fuse is normal:

― Repair or replace the wiring harness for a possible open circuit.

Go to the next step.

6

VERIFY TROUBLESHOOTING COMPLETED

• Make sure to reconnect the disconnected connectors.

• Reconnect the negative battery cable.

(See BATTERY REMOVAL/INSTALLATION [MZR 1.5, MZR 1.6].)

(See BATTERY REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)

(See BATTERY REMOVAL/INSTALLATION [MZR 2.0 DISI i-stop].)

(See BATTERY REMOVAL/INSTALLATION [MZR 2.3 DISI Turbo].)

(See BATTERY REMOVAL/INSTALLATION [MZR-CD 2.2].)

(See BATTERY REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

• Operate the advanced key to activate the keyless control module.

• Clear the DTC from the keyless control module using the M-MDS.

(See CLEARING DTC [ADVANCED KEYLESS ENTRY AND PUSH BUTTON START SYSTEM].)

• Operate the advanced key to activate the keyless control module.

• Perform the advanced keyless entry and push button start system DTC inspection using the M-MDS.

(See DTC INSPECTION [ADVANCED KEYLESS ENTRYAND PUSH BUTTON START SYSTEM].)

• Is the same DTC present?

Yes

Replace the keyless control module, then go to the next step.

(See KEYLESS CONTROL MODULE REMOVAL/INSTALLATION.)

NoGo to the next step.

7VERIFY THAT NO OTHER DTCs ARE PRESENTYesGo to the applicable DTC inspection.

StepInspectionAction

• Are any DTCs present?

(See DTC TABLE [ADVANCED KEYLESS ENTRY AND PUSH BUTTON START SYSTEM].)

NoDTC troubleshooting completed.

DTC P1794:17 [ADVANCED KEYLESS ENTRY AND PUSHBUTTON START SYSTEM]

id09021c933200

DESCRIPTIONHigh voltage in power supply circuit (+B2)

DETECTION CONDITION• Keyless control module power supply circuit (+B2) voltage is 16.5 V or more for 0.5 s.

POSSIBLE CAUSE

• PCM DTC is stored

• Generator malfunction

• Keyless control module malfunction

Diagnostic Procedure

StepInspectionAction

1

CONFIRM PCM DTC

• Perform the PCM DTC inspection using the M-MDS.

(See ON-BOARD DIAGNOSTIC TEST [MZR 1.5, MZR 1.6].)

(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0, MZR 2.5].)

(See ON-BOARD DIAGNOSTIC TEST [MZR 2.0 DISI i-stop].)

(See ON-BOARD DIAGNOSTIC TEST [MZR 2.3 DISI Turbo].)

(See ON-BOARD DIAGNOSTIC TEST [MZR-CD 2.2].)

(See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0].)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [MZR 1.5, MZR 1.6].)

(See DTC TABLE [MZR 2.0, MZR 2.5].)

(See DTC TABLE [MZR 2.0 DISI i-stop].)

(See DTC TABLE [MZR 2.3 DISI Turbo].)

(See DTC TABLE [MZR-CD 2.2].)

(See DTC TABLE [SKYACTIV-G 2.0].)

NoGo to the next step.

2INSPECT GENERATOR

• Inspect the generator.

(See GENERATOR INSPECTION [MZR 1.5, MZR 1.6].)

(See GENERATOR INSPECTION [MZR 2.0, MZR 2.5].)

YesReplace the generator, then go to the next step.

(See GENERATOR REMOVAL/INSTALLATION [MZR 1.5, MZR 1.6].)

(See GENERATOR REMOVAL/INSTALLATION [MZR 2.0, MZR 2.5].)

StepInspectionAction

(See GENERATOR INSPECTION [MZR 2.0 DISI i-stop].)

(See GENERATOR INSPECTION [MZR 2.3 DISI Turbo].)

(See GENERATOR INSPECTION [MZR-CD 2.2].)

(See GENERATOR INSPECTION [SKYACTIV-G 2.0].)

• Is there any malfunction?

(See GENERATOR REMOVAL/INSTALLATION [MZR 2.0 DISI i-stop].)

(See GENERATOR REMOVAL/INSTALLATION [MZR 2.3 DISI Turbo].)

(See GENERATOR REMOVAL/INSTALLATION [MZR-CD 2.2].)

(See GENERATOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

NoGo to the next step.

3

VERIFY TROUBLESHOOTING COMPLETED

• Operate the advanced key to activate the keyless control module.

• Clear the DTC from the keyless control module using the M-MDS.

(See CLEARING DTC [ADVANCED KEYLESS ENTRY AND PUSH BUTTON START SYSTEM].)

• Operate the advanced key to activate the keyless control module.

• Perform the advanced keyless entry and push button start system DTC inspection using the M-MDS.

(See DTC INSPECTION [ADVANCED KEYLESS ENTRY AND PUSH BUTTON START SYSTEM].)

• Is the same DTC present?

Yes

Replace the keyless control module, then go to the nextstep.

(See KEYLESS CONTROL MODULE REMOVAL/INSTALLATION.)

NoGo to the next step.

4VERIFY THAT NO OTHER DTCs ARE PRESENT

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [ADVANCED KEYLESS ENTRY ANDPUSH BUTTON START SYSTEM].)

NoDTC troubleshooting completed.

P1884 CADILLACP1884 CADILLAC - TCC Enable/Shift Light Circuit

P1797P1797 - Neutral Switch Circuit Malfunction

Possible symptoms- Engine Light ON (or Service Engine Soon Warning Light)

P1797: Clutch Pedal Position Switch Or Neutral Switch Malfunction

Definition of Diagnostic Trouble Code P1797

Audi:

Vehicle Speed Signal Circuit Short to B+

Chrysler:

Manual Shift Overheat

Dodge:

Manual Shift Overheat

Ford:

Neutral Switch Circuit

Jaguar:

CAN TCM/ECM Circuit Malfunction

Jeep:

Manual Shift Overheat

Kia:

P or N Range Signal or CPP Switch Open or Short

Lincoln:

Neutral Switch Circuit

Mazda:

Clutch Pedal Position Switch/Neutral Switch Circuit

Mercury:

Neutral Switch Circuit

Volkswagen:

Vehicle Speed Signal Circuit Short to B+

Latest News

Automotive Electro-Mechanical Relays Types / Faults / Diagnosis May 2013

We need to relay this important information

With the amount of electrical components and controls now fitted to the modern vehicle, it is important that the targeted load is supplied with the necessary voltage / current as required to ensure continuous, uninterrupted operation.

That is, to reduce voltage drop to the component during broad temperature changes and high vibration in all climate operation. As an example, whether it’s a radiator cooling fan, an air conditioning compressor or a starter motor, any relay interruption may cause at least an uncomfortable journey or possibly a trip on the tow truck. All this from a low cost, readily

available, easily tested and replaced, small but important component that gets generally verbally abused when it fails. Ask me how I know.

Let’s look at the types of vehicle relays and the importance of fitting the correct replacement

Typical commonly used automotive types.

Mini Relays – electromechanically operated contact switches. May be 4 pin / 5 pin or 6 pin configuration.

The 4 pin configuration may either be:

A Normally open (NO) relay where the internal mechanical contacts are held open when the relay is in a disconnected state. The contacts close when activated. This is the most common type found on the vehicle. A specifically produced power relay may resemble this unit but is manufactured for switching nominal current of 50A or more, making them suitable as operating relays for starting motors, glow plug operation, motor relay for antilock braking systems, to name a few.

A normally closed (NC) relay where the internal mechanical contacts are held closed when the relay is in a disconnected state.

The 5 pin configuration may be:

A Change over relay where 2 sets of contacts are used with one set normally open and the other set normally closed. These of course will alternate once the relay is activated. This type of relay will generally display 2 current ratings (for each contact circuit) and it is important that a replacement relay unit is matched to the original relay specifications.

A Normally open, dual output 5 pin relay

But wait there’s more.

Even on these common relay types there are more variations and features and fitting any old relay is not an option.

Resistor protected or Diode Protected

Terminals 36 and 86 exchanged

Amperage variations and variations in contact material.

Micro Relays

These units are ideal, due to their size, for space restricted areas. The micro relays vary in pin configuration to the mini relays but are still available in 4 and 5 pin with similar variations and features.

Pin identification may vary to the mini relays as follows.

Faults/ Diagnosis/Testing.

The relay may intermittently fail under certain conditions or fail totally. This may be confused with harness or socket terminal faults so it is important to correctly verify the fault.

Simple test equipment is available to quickly identify some circuit or relay faults and carry out time saving quick tests.

We need to get excited about it.

A common occurring vehicle system fault is the lack of relay winding excitation that can stop the relay functioning and can cause the vehicle to stall. A typical example may be the petrol fuel pump relay which switches off whilst driving that is causedby a fault in the ECM and not in the relay itself.

Renewing the relay and sending the vehicle on its way is not a thorough test. Unfortunately, by the time the Technician has been called out and proceeds to carry out any tests on the vehicle the ECM has cooled down and may function normally. Thorough testing again is required to pin point the area of concern.

Simple test equipment again may assist the Technician to carry out this task. Bridging relay socket pins for the inexperiencedor semi educated may result in damage or unrepairable damage to the fuel pump control circuit in the ECM. You may be surprised on how many times this has occurred. Then again you may not!

P1306P1306 - Kickdown Relay Pull In Circuit Fault

Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

P1306 Description

Kickdown Relay Pull In Circuit Fault is one of the definitions for the P1306; however your vehicle's manufacturer may have a different definition for the P1306 code. Please check below for your specific make.

P1306 FORDP1306 FORD - Kickdown Relay Pull In Circuit Fault

Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

Alan ==========

I made a schematic annotation to help power flow:

Theo

1992 Porsche 928 GTS midnight blue

The Netherlands

Kickdown relay (two versions, this is the pre-1989, starting 1989 the relay has extra inputs)

What is the sole purpose of kickdown switch relay and how will I know that it is malfunctioning?

Bora Ertung

==========================================

Hello Bora, The kick-down switch closes a circuit to the automatic transmission and forces adownshift to the lowest possible gear for the speed/RPM of the car. A relay is a switch, with the"open/close" controlled by a relatively small current compared to the amount of current flowing

through the actual switch. A relay is used when it is desirable to control a large amount of currentwith a small current. The kick-down switch (and wires) at the throttle are small compared to what

would be necessary to manage the solenoids in the transmission. If the kick-down relay isn'tworking, you will see two possible scenarios; - if it is stuck in the open position, you get no kick-

down when stomping the throttle petal to the floor - if it is stuck closed, you will always be in kick-down mode and will have a much too aggressive shift program for normal driving (always revving

to near the redline prior to upshift) My guess is being stuck in the closed position would be rare.

Rich

2 928's with kick-down switches

============================================

For all those auto. trans. out there. I installed a temporary switch to bypass the kickdown processfor my '85. I've read a few messages on the list that extoll the new found gitty-up that there cars

seem to have at lower speeds without having to put the pedal through the floor. Well, after Iscrewed up a $10 job, (pinched wire = meltdown), I had my mechanic go through it, (now $200 job

w/wire harness, accordion conduit around the wires etc.), and it is functional. However, the onlyreal benefit I have found is at the higher cruising speeds where if you need to pass, with a simplepress of this button, (mine is on the left footpad), it shifts down into 3rd for that added response.But that is it! From what I read on the list, I was expecting it to send it to 1st or 2nd for that true

"kickdown" efect. It absolutely had no benefit for freeway onramp acceleration. Am I missingsomething? Thanks,

Rory Hart '85S A/T

==============================================

Dear Roy: On my previous 86 928S AT I installed a parallel kick down switch. When pressed once itwas on. To turn it of, it had to be pressed again. During autocrosses I would "set it, and forget it." I

was always in the lowest possible gear that did not exceed redline. During DE, I prefer to determinethe gear I want on my own, so it rarely was used. For street use, it was good for a few low speedthrills, but not often. Besides my mileage was not great to begin with, and using it made it much

worse. The fact that your AT is not shifting down to the lowest gear possible may indicate there areother problems. Try the following experiment. First, do not use the kick-down switch at all. Second,

from a standing start, place the gear selector in "2". Accelerate slowly to 25 MPH (40 KPH) and takenotice of the Tach. (You should be in 1st gear). When you get to 4,000 RPM move the selector to "3"

and back to "2" quickly. (You should now be in 2nd gear.) Continue to accelerate and at 3,000 RPMmove the selector to "3" and leave it there. (You should be in 3rd gear.) Finally, move the selector

to "D". You should now be in 4th. Merry motoring. ~Ed~

=============================================

At 08:46 PM 7/24/01, Dennis Wilson wrote:

<I recently tried doing the "kickdown switch modification" as documented on many sites. Resultwas no discernable change in shifting behavior. After checking my connections and ensuring thetoggle switch is really switching the circuit (probing continuity across the foot switch connector),I'm fairly sure there is nothing wrong with my wiring job. That leaves me to suspect faults in howthis circuit is sending control signals to the AT. I think I'm in for some under-car exploration... Has

anyone BTDT? I'm guessing there may be some kind of relay involved.

<Anyone know how/where the kickdown circuit connects to the AT?

<TIA dw

As usual, it would have been nice to know the specific year model, but....

The automatic transmission is primarily controlled by internal hydraulic pressures. This includes thespeed at which up shifts and downshifts occur, and the firmness of the shifts.

The kickdown solenoid is only one of several devices that adjust the control pressure to change theshifts. When the kickdown switch is made (closed), power flows from fuse #10 (on the '87) thru the

switch, then into the 30 terminal of the kickdown relay (XV on the '87), thru the normally closedcontacts of the relay, and out the 87a terminal to the kickdown solenoid mounted inside the

transmission. When the solenoid is energized, it reduces control pressure, raising the shift speedclose to the maximum speed.

The kickdown relay doesn't do what most people think that it does. The power flow from the switchto the solenoid is thru the NORMALLY CLOSED contacts of the relay. This means that the power

normally flows thru the relay. In order to control the shift points more precisely (since the speed isvery close to engine redline), the kickdown relay receives a signal from the tachometer when

engine speed hits 5800 +/-60 RPM (USA and Japan - it's 100 RPM higher for the ROW). This signalopen the contacts in the kickdown relay, breaking the power to the kickdown solenoid. This has thesame efect as instantaneously lifting your foot from the throttle switch, causing an instant shift. Assoon as the engine speed goes back below 5800, the relay closes the contacts, lowering the control

pressure to hold the next shift.

So, the kickdown switch (and the added parallel kickdown switch) supplies power to the kickdownsolenoid only when the engine speed is below 5800 RPM. Above that speed, the kickdown relay

opens, breaking the circuit .

You can check by pulling relay XV (on the '87) and jumpering terminals 30 and 87a in the socket,then driving the car. If there is now a diference in the shift speeds, relay XV or the contacts for it

are bad.

I would suggest that you NOT try the full throttle shift points with the relay jumpered.

Wally Plumley

928 Specialists

===========

I recently learned more about the kick down relay operation (even though I don't have one). It isnot intuitive.

The relay is not activated by the switch (or a bypass installed instead). Instead it is activatedvariously over the years by engine RPM, throttle position, speed, dynamic throttle inputs.(

The relay terminals are normally closed and the solenoid is activated directly by the kick downswitch (or bypass) though these normally closed contacts. When the solenoid is activated the AT

control pressure is lowered & the shift point speeds are raised.

The kick down relay is activated primarily by an engine RPM signal (at high RPM points - from dash)which causes the relay to turn of the solenoid - this is what causes the shift to happen - which itself

causes the RPM to drop and reengages the solenoid to hold the next gear until it gets to high RPMagain...

So bottom line is you will engage the solenoid almost full-time if your kick down is alwaysactivated/bypassed. It does not seem to be a major reliability factor since I haven't seen reports ofsolenoid failure and as far as I can see its just operating a pressure relief valve so is probably quite

low power ...

So in summary:

The kick down switch causes the trans to hold in gear to higher RPM/speed .

The relay momentarily breaking the connection causes the high RPM shifts to happen.

I do also think a (left) foot operated momentary switch is probably the best option to control this.

Alan

__________________

1994 928 GTS Black/Black Manual "AZ Desert Gang"

=========

Hello Alan

I didn't realize that the relay has normally closed contacts. What I said earlier should have morecorrectly stated "Looking at the circuit, the KD switch applies battery volts to the 12v side of the

CONTACTS of the kick down relay ."

So as I understand it, the KD relay may be opening its contacts at some predetermined rpm butuntil the KD switch is bypassed or normally activated then the KD relay can't activate the gearbox

solenoid because there are no volts available to energize it (and then allow the relay to break thosesupply volts)

Do you agree ?

__________________

John '86 Euro S2

==========

Yes - the KD relay is actually more of an "anti K-D" relay in most versions. Its job is only to disablethe kick-down when the trans should shift or before a min speed has been reached. This is what is

not intuitive at all about it - it works quite opposite to the switch.

Only in the GTS dynamic kick-down can the relay actually activate the solenoid itself. In that case itstill retains the disable function - its just as if there is now also a parallel kick-down switch inside

the relay. The schematics for the later relay do not show this extra contact set - but they must bethere.

Alan

=========

new TPS & New KD relay and a bit of additional wiring - 1 new wire between the new TPS & therelay should get you exact GTS 94+ behavior. Actually not that hard to do electrically (but you have

to pull the intake to swap the TPS. Its a little more complex on 88 and older...

See http://forums.rennlist.com/rennforums/showthread.php?t=245964

Alan

==========

I made a schematic annotation to help understanding the kickdown relay power flow:

Electronic Transmissions

Copyright AA1Car Adapted from an article written by Larry Carley for Underhood Service magazine

Todays electronic transmissions use sensors, solenoids and relays to regulate the operation of the clutches, gears and torque converter. On applications where these functions have not been integrated into the powertrain control module (PCM), there is a separate transmission control module (TCM) to oversee the operation of the transmission - and that is the focus of this article: how TCMs and PCMs interact.

Just like the PCM, the TCM needs accurate information to do its job properly. If the transmission computer receives bad information from the transmissions own internal sensors or bad inputs from the PCM or other engine sensors, it will have an adverse effect on how the transmission operates. It may not shift smoothly. It may shift at the wrong rpm. It may even go into a "limp-in" mode and remain frozen in second or third gear.

Essential InformationElectronic transmissions are getting smarter all the time. Most of the current generation units have fully adaptive control systems that "learn" the best shift points based on real-time sensor inputs and feedback. The transmission computer adapts the shift strategy to compensate for changes in engine performance and wear in the transmission friction elements in the clutches. By making subtle changes to the shift points and engagement, the computer tries to maintain consistent shift quality.

The transmission computer monitors what is happening inside the transmission with various speed and gear range sensors that tell it if the gears are shifting correctly and at what speeds. But to pick the shift points, it needs certain inputs from the engine and PCM. The transmission computer needs to know how fast the vehicle is traveling. This information is provided by

the vehicle speed sensor. It also needs to know engine speed (rpm) and load .

On some applications, the rpm signal is hard-wired directly to the transmission computer as well as the PCM. There is a dedicated circuit between the crankshaft position sensor and TCM to supply the rpm signal. On other applications, the rpm signal goes only to the PCM and the PCM forwards it to the TCM via a data bus circuit.

Engine load can be determined from throttle position, intake vacuum and airflow. Depending on what type of fuel injection system is used (speed density or airflow), engine load inputs may come from the throttle position sensor (TPS), manifold absolute pressure sensor (MAP) and/or a vane airflow sensor (VAF) or mass airflow sensor (MAF). As with the rpm signal, the information may be shared directly with the transmission computer or it may go through the PCM and forwarded to the TCM over the data bus.

Effects of Bad Engine Sensor Inputs on the Transmission

Because the transmission needs to know engine speed and load as well as vehicle speed to pick the right shift points, a bad sensor input or loss of a signal can create real problems for the transmission computer.

The throttle position sensor signal takes the place of the throttle kickdown linkage on older mechanical automatics. So if the TPS is reading high or low, or has a dead spot, it can affect transmission kickdown shifts when accelerating, as well as normal upshifts and downshifts, too. If the TCM cannot get a good TPS signal, it may substitute a "calculated" throttle angle provided by the PCM over the data bus. Or, if this signal is not available, it may substitute a fixed value for the TPS signal. This will obviously affect the way it shifts (transmission typically hunts for shift points) but not necessarily cause it to go into a limp-in mode.

A faulty throttle position sensor will not always set a fault code. The PCM has to be smart enough to figure out when the TPS is working properly and when it is not. Its diagnostic strategies may compare the TPS signal against engine rpm, MAP signal and/or airflow to determine if the TPS signal makes sense. If the TPS signal does not correspond to other sensor inputs that can be used to measure engine load, the PCM may set a fault code. Then again, it might not. It all depends on the self-diagnostic strategy, how sensitive it is to faults and how easily the PCM can detect problems.

Transmission Limp-In ModesUnder certain conditions, which may include the loss of one or more vital inputs to the TCM, the transmission will go into some kind of limp-in or "default" mode. When a serious fault is diagnosed (such as loss of an internal speed sensor signal) ora problem occurs in the wiring circuit to any of the shift solenoids, the TCM will kill the power to the transmission control relayand deenergize all of the shift solenoids. This usually causes the transmission to freeze in 2nd or 3rd gear. The transmission will remain in limp-in mode until (1) the problem is diagnosed and repaired, or (2) power to the TCM is momentarily turned offto "reset" the computer. This may restore normal operation temporarily, but as soon as the TCM detects the fault again, it will go back into limp-in mode.

Transmission Diagnostic Trouble Codes

Like PCMs, TCMs have the ability to self-diagnose faults and set diagnostic trouble codes that can be read with a scan tool. So if the Malfunction Indicator Lamp (MIL) is on and the transmission is not operating properly, the fault may be in the transmission - or it may be in the engine. The only way to find out is to pull the code(s) to see what is going on.

It is not unusual to blame some engine driveability problems on the transmission and vice versa. A torque converter that locks up prematurely or fails to release quickly enough can cause a driveline shudder that may feel like an engine misfire or vibration. If the torque converter fails to release at all, it can cause the engine to buck and stall when coming to a stop.

Any time you encounter a problem with an electronic automatic or find a transmission code, make sure the engine is running properly and there are no engine codes that could affect the operation of the transmission. In other words, take care of any engine problems first before attempting to diagnose a transmission problem.

If a vehicle has a data bus communication problem between the TCM and PCM, you probably will not be able to access any transmission codes until the wiring problem is fixed. Possible causes include an open or short to the ground or battery in the PCI bus circuit, or an internal failure of any module or component that is attached to the bus.

The data bus is monitored any time the ignition key is on. If no messages are received from the PCM for 10 or more seconds, it tells the TCM something is wrong and it sets a data bus code.

If the transmission can find an engine speed signal from the crankshaft position sensor or PCM, the transmission can be forced into the limp-in mode. The problem should set a crank sensor circuit fault code and turn on the MIL. Possible causes include an open or short in the crank sensor circuit, a TCM connector problem, an open or short in the crank sensor ground circuit, or an internal fault in the TCM or PCM.

On OBD II applications, various transmission codes are included in the "generic" list of OBD II codes. If the transmission computer detects a problem that may affect emissions, it will send a request over the data bus to the engine computer to turn on the MIL lamp. A code will be set inthe TCM and remain there until it is cleared or no fault is detected during 40 consecutive drive cycles. The MIL may go out

but leave the code in memory if no fault is detected during three consecutive drive cycles .

Illustration Courtesy of ZF Friedrichshafen AG

Seven Steps for Troubleshooting An Electronic Automatic TransmisionThe recommended procedure for troubleshooting an electronic automatic transmission problem involves seven steps:

1. Verify the complaint. Is the transmission really shifting improperly, shuddering, slipping, etc.?

2. Verify any related symptoms. Is the engine overheating, are there engine fault codes or other driveability problems?

3. Analyze the symptoms and when they occur. Does the complaint only occur when hot, cold, driving at certain speeds, etc.?

4. Check for any OEM technical service bulletins that might apply to the problem.

5. Isolate the fault. Use the trouble codes and diagnostic charts to narrow down the possibilities. Is the problem inside or outside the transmission. Is it hydraulic, mechanical or electronic?

6. Repair the fault. Replace the faulty component, replace the transmission or repair the wiring fault.

7. Verify the repair. Did you fix the problem?