1998 f-150/250 workshop manual page 1 of 74

Transfer Case—ESOF

Refer to Wiring Diagrams Cell 34, Electric Shift Control for schematic and connector information.

Refer to Wiring Diagrams Cell 20, Starting System for schematic and connector information.

Refer to Wiring Diagrams Cell 59, Generic Electronic Module for schematic and connector information.

Electrical Shift on the Fly (ESOF) Vacuum Schematic

4WD Tables

Table 1 — 4WD Mode Switch Input Resistances

SECTION 308-07A: Transfer Case — General Information 1998 F-150/250 Workshop Manual

DIAGNOSIS AND TESTING Procedure revision date: 12/04/2002

Special Tool(s)

73 Digital Multimeter or equivalent 105-R0051

New Generation STAR (NGS) Tester or equivalent 418-F048 (007-00500)

Vacuum Pump or equivalent 416-D001 (D83L-7059-A)

of 741998 F-150/250 Workshop Manual

1/11/2011http://www.fordtechservice.dealerconnection.com/pubs/con...

Table 2 — Transfer Case Shift Relays Outputs

Table 3 — Neutral Safety Switch Input Conditions

Table 4 — Contact Plate Sensor Position Codes

* Refers to the code at the point of transition between two positions or areas of the sensor.

Inspection and Verification — Electronic Shift on the Fly (ESOF

1. Verify the customer concern by operating the 2WD/4WD engagement.

2. Visually inspect for the following obvious signs of mechanical and electrical damage.

Visual Inspection Chart

3. If the concern remains after the inspection, connect the New Generation STAR (NGS) Tester to the data link connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the NGS menu. If the NGS does not communicate with the vehicle:

� check that the program card is properly installed.

� check the connections to the vehicle.

� check the ignition switch position.

4. If the NGS still does not communicate with the vehicle, refer to the New Generation STAR Tester manual.

5. Perform the DATA LINK DIAGNOSTIC TEST. If the NGS responds with:

� CKT914, CKT915 or CKT70 = ALL ECUS NO RESP/NOT EQUIP, refer to Section 418-00.

� NO RESP/NOT EQUIP for GEM, go to Pinpoint Test F.

� SYSTEM PASSED, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and perform self-test diagnostics for the GEM.

6. If the DTCs retrieved are related to the concern, go to the GEM Diagnostic Trouble Code (DTC) Index to continue diagnostics.

7. If no DTCs related to the concern are retrieved, proceed to Symptom Chart to continue diagnostics.

GEM Diagnostic Trouble Code (DTC) Index

Mode Switch Position Resistance (Ohms)

2-Wheel Drive 4100-3700

4WD HIGH 1050-1150

4WD LOW 380-340

HI-to-LO LO-to-HI Mode

GROUND BATTERY 4 HIGH to 4 LOW

BATTERY GROUND 4 LOW to 4 HIGH

GROUND GROUND Brake Motor

Transmission State Start/Clutch Depressed Input Neutral Safety Switch Input

In Gear Open Open

Park Ground Open

Neutral Ground Ground

(Start) Park Battery Voltage Open

(Start) Neutral Battery Voltage Ground

Contact Plate Code Left Mech .Stop Left Stop 2H 2H E* 4H *E 4H 4L *E 4L Right Mech .Stop

A Closed Closed Closed Closed Closed Open Open Open Closed

B Open Open Open Closed Closed Closed Closed Closed Closed

C Open Closed Closed Closed Closed Closed Closed Open Open

D Open Open Closed Closed Open Open Closed Closed Closed

Mechanical Electrical

� Switch(es) � Fuse(s) � Damaged wiring harness � Loose or corroded connector(s) � Circuitry



GEM Diagnostic Trouble Code (DTC) Index

DTC DescriptionDTC

Caused By Action

B1302 Accessory Delay Relay Coil Open or Short to Ground (Only Set if Battery Saver Relay Has No Faults)

GEM REFER to Section 501-11.

B1304 Accessory Delay Relay Coil Short to Power GEM REFER to Section 501-11.

B1313 Battery Saver Relay Coil Open or Short to Ground GEM REFER to Section 417-02.

B1315 Battery Saver Relay Coil Short to Power GEM REFER to Section 417-02.

B1317 Battery Voltage HIGH, Greater Than 18.0 Volts GEM REFER to Section 414-00.

B1318 Battery Voltage LOW, Less Than 10 Volts GEM REFER to Section 414-00.

B1322 LF Door Open Warning Circuit Short to Ground, or Door Open


B1323 Door Open Warning Lamp Open or Short to Ground GEM REFER to Section 413-01A or Section 413-01B.

B1325 Door Open Warning Lamp Short to Power GEM REFER to Section 413-01A or Section 413-01B

B1330 RF Door Open Warning Circuit Short to Ground, or Door Open


B1342 ECU is Defective, RAM/ROM Checksum Failure GEM CLEAR the DTCs. RETRIEVE the DTCs. If DTC B1342 is retrieved, REPLACE the GEM. REFER to Section 419-10. TEST the system for normal operation.

B1352 Key-in-Ignition Circuit Open GEM REFER to Section 413-09.

B1355 Ignition RUN Circuit Open GEM REFER to Section 211-05, Symptom Chart.

B1359 Ignition RUN/ACC Circuit Open GEM REFER to Section 211-05, Symptom Chart.

B1365 Ignition START Circuit Short to Power GEM REFER to Section 211-05, Symptom Chart.

B1371 Interior Lamp Relay Coil Open or Short to Ground GEM REFER to Section 417-02.

B1373 Interior Lamp Relay Coil Short to Power GEM REFER to Section 417-02.

B1398 LF One-Touch Down Power Window Relay Coil Open or Short to Ground


B1400 LF One-Touch Down Power Window Relay Coil Short to Power


B1405 LF Power Window Switch Down Circuit Short to Power GEM REFER to Section 501-11.

B1408 LF Power Window Switch Up Circuit Short to Power GEM REFER to Section 501-11.

B1410 LF Power Window Motor Excessive Current Draw GEM REFER to Section 501-11.

B1426 Safety Belt Lamp Circuit Short to Power GEM REFER to Section 413-01A or Section 413-01B.

B1428 Safety Belt Lamp Circuit Open or Short to Ground GEM REFER to Section 413-01A or Section 413-01B.

B1431 Wiper RUN/PARK Relay Coil Circuit Open or Short to Ground


B1432 Wiper RUN/PARK Relay Coil Circuit Short to Power GEM REFER to Section 501-16.

B1434 Wiper HI/LO Speed Relay Coil Circuit Open or Short to Ground


B1436 Wiper HI/LO Speed Relay Coil Circuit Short to Power GEM REFER to Section 501-16.

B1438 Wiper Mode Select Switch Open or Short to Power GEM REFER to Section 501-16.

B1441 Wiper Mode Select Switch Circuit Short to Ground GEM REFER to Section 501-16.

B1446 Wiper Motor PARK Sense Circuit Short to Ground GEM REFER to Section 501-16.

B1450 Wiper Interval Delay Switch Circuit Open or Short to Power GEM REFER to Section 501-16.

B1453 Wiper Interval Delay Switch Circuit Short to Ground GEM REFER to Section 501-16

B1458 Washer Pump Motor Relay Coil Circuit Open or Short to Ground


B1460 Washer Pump Motor Relay Coil Short to Power GEM REFER to Section 501-16.

B1462 Safety Belt Switch Circuit Open GEM REFER to Section 413-09.

B1466 Wiper HI/LO Speed Not Switching GEM REFER to Section 501-16.

B1467 Wiper HI/LO Speed Motor Circuit Short to Power GEM REFER to Section 501-16.

B1473 Wiper LO Speed Motor Circuit Failure (Wiper Energized and Park Sense Not Seen)


B1476 Wiper LO Speed Motor Circuit Failure (Wiper Energized and Park Sense Not Seen)


B1483 Brake Pedal Input Open Circuit (No Brake Input Seen For 8 Ignition Cycles)

GEM GO to Pinpoint Test B.

B1485 Brake Pedal Input Circuit Short to Battery GEM GO to Pinpoint Test B.

B1577 Headlamp/Parking Lamp Input Circuit Short to Power GEM REFER to Section 417-01.

B1610 Illuminated Entry Input Short to Ground GEM REFER to Section 417-02.

B1840 Wiper Power Circuit Failure GEM REFER to Section 501-16.

P0500 Vehicle Speed Signal Not Detected GEM GO to Pinpoint Test B.

P1804 4-Wheel Drive HI Indicator Open or Short to Ground GEM GO to Pinpoint Test C.

P1806 4-Wheel Drive HI Indicator Short to Power GEM GO to Pinpoint Test C.

P1808 4-Wheel Drive LO Indicator Open or Short to Ground GEM GO to Pinpoint Test C.



GEM Parameter Identification (PID) Index

GEM Parameter Identification (PID) Index

P1810 4-Wheel Drive LO Indicator Short to Power GEM GO to Pinpoint Test C.

P1812 4-Wheel Drive Mode Select Switch Open or Short to Power GEM GO to Symptom Chart.

P1815 4-Wheel Drive Mode Select Switch Circuit Short to Ground GEM GO to Symptom Chart.

P1819 Neutral Safety Switch Input Short to Ground GEM GO to Pinpoint Test B.

P1820 Transfer Case LO to HI Shift Relay Coil Open or Short to Ground

GEM GO to Pinpoint Test A.

P1822 Transfer Case LO to HI Shift Relay Coil Short to Power GEM GO to Pinpoint Test A.

P1824 4-Wheel Drive Electric Clutch Relay Open or Short to Ground

GEM GO to Pinpoint Test E.

P1826 4-Wheel Drive Electric Clutch Relay Short to Power GEM GO to Pinpoint Test E.

P1828 Transfer Case HI to LO Shift Relay Open or Short to Ground

GEM GO to Pinpoint Test A.

P1830 Transfer Case HI to LO Shift Relay Short to Power GEM GO to Pinpoint Test A.

P1832 Front Axle 4-Wheel Drive Solenoid Open or Short to Ground

GEM GO to Pinpoint Test C.

P1834 Front Axle 4-Wheel Drive Solenoid Short to Power GEM GO to Pinpoint Test C.

P1838 Transfer Case Shift Motor Fails to Move (Energized Relays, Motor Does Not Move)

GEM REFER to Section 308-07A.

P1846 Transfer Case Contact Plate A Open Circuit GEM GO to Symptom Chart.

P1850 Transfer Case Contact Plate B Open Circuit GEM GO to Symptom Chart.

P1854 Transfer Case Contact Plate C Open Circuit GEM GO to Symptom Chart.

P1858 Transfer Case Contact Plate D Open Circuit GEM GO to Symptom Chart.

P1866 Transfer Case System Concern, Contact Plate Failure GEM GO to Symptom Chart.

P1867 Transfer Case Contact Plate Open or Short to Ground GEM GO to Symptom Chart.

P1876 Transfer Case 2-Wheel Drive Solenoid Open or Short to Ground

GEM GO to Pinpoint Test C.

P1877 Transfer Case 2-Wheel Drive Solenoid Short to Power GEM GO to Pinpoint Test C.

P1891 Transfer Case Contact Plate Ground Return Open Circuit GEM GO to Symptom Chart.

PID Description Expected Values

ACCDLY Accessory Delay Relay Coil Circuit ON---, OFF---, ON-B-, OFFO-G

AXL_DIS 4WD Center Axle Disconnect ON---, OFF---, ON-B-, OFFO-G

AXLSTAT 4WD Center Axle Disconnect ON, OFF

BATSAV Battery Saver Relay Circuit ON---, OFF---, ON-B-, OFFO-G

BOO_GEM Brake Pedal Position (BPP) Switch Input ACTIVE, notACT

CLTCHSW Clutch Pedal Position (CPP) Switch ACTIVE, notACT

D_DN_

SW

Window Regulator Control Down Switch State OFF, DOWN

D_UP_

SW

Window Regulator Control Up Switch State OFF, UP

D_PWRLY One Touch Down Relay Coil Circuit Status OFF, ON

D_

PWAMP

Window Regulator Electric Drive Motor Current 0.25 amp increments

D_PWPK Window Regulator Electric Drive Current 0.25 amp increments

DRAJAR_L Door Ajar Indicator Circuit ON---, OFF---, ON-B-, OFFO-G

D_DR_SW LH Door Open Warning Lamp Switch CLOSED, AJAR

D_SBELT LH Safety Belt IN, OUT

HALLPWR Hall Effect Speed Sensor Power ON---, OFF---, ON-B-, OFFO-G

ILLE_SW Illuminated Entry Input (From RAP Module) ON, OFF

IGN_GEM Ignition Switch States START, RUN, OFF, ACCY

IGN_KEY Ignition Key-In/Out IN, OUT

INTLMP Interior Lamp Relay Circuit ON---, OFF---, ON-B-, ONO-G

MTR_CCW HI to LO Shift Relay Coil Status ON---, OFF---, ON-B-, OFFO-G

MTR_CW LO to HI Shift Relay Coil Status ON---, OFF---, ON-B-, OFFO-G

NTRL_SW Transmission Range Sensor Input NTRL, notNTRL

OTD_SW One Touch Down Switch State OFF, DOWN

P_DR_SW RH Door Open Warning Lamp Switch CLOSED, AJAR



GEM Active Command Index

GEM Active Command Index

Symptom Chart — Electronic Shift on the Fly (ESOF)

PARK_SW Headlamp Control Input Switch ON, OFF

PLATE_A Transfer Case Contact Plate Switch A OPEN, CLOSED

PLATE_B Transfer Case Contact Plate Switch B OPEN, CLOSED

PLATE_C Transfer Case Contact Plate Switch C OPEN, CLOSED

PLATE_D Transfer Case Contact Plate Switch D OPEN, CLOSED

PLATEPW Contact Plate Ground Output ON, OFF

SBLTMP Safety Belt Warning Indicator ON---, OFF---, ON-B-, OFFO-G

SPEEDWP Speed Dependent Wiper Function ACTIVE, notACT

VBATGEM Battery 0.1 Volt DC per count

VSS_GEM Vehicle Speed Sensor 0-255 KPH

WASHRLY Washer Pump Relay Circuit ON---, OFF---, ON-B-, OFFO-G

WASH_SW Washer Relay Output ON---, OFF---, ON-B-, OFFO-G

WPHISP Wiper HI/LO Relay Status ON---, OFF---, ON-B-, OFFO-G

WPMODE Wiper/Washer Switch Status WASH, OPEN, INVLD, OFF, INTVL 1-7, LOW, HIGH

WPPK_PK Wiper Park to Park Time 0 to 65 ms

WPPRKSW Wiper Motor Switch Status PARKED, notPRK

WPRUN Wiper Run/Park Relay Status ON---, OFF---, ON-B-, OFFO-G

2WDSOL 2WD Solenoid Status ON---, OFF---, ON-B-, OFFO-G

4WDCLST Four Wheel Drive Clutch Relay Control ON---, OFF---, ON-B-, OFFO-G

4WDHIGH 4WD High Indicator Status ON---, OFF---, ON-B-, OFFO-G

4WDLOW 4WD Low Indicator Status ON---, OFF---, ON-B-, OFFO-G

4WDSGEM 4WD Mode INVLD, 2WD, 4WDLOW, 4WDHIGH, OFFO-G

4WDSOL 4WD Solenoid Status ON---, OFF---, ON-B-, OFFO-G

Active Command Display Action

PID LATCH PID LATCH ON, OFF

WINDSHIELD WIPER WIPER RLY ON, OFF

WINDSHIELD WIPER SPEED RLY ON, OFF

WINDSHIELD WIPER WASH RLY ON, OFF

WARNING LAMPS AND CHIME SBLT LAMP ON, OFF

WARNING LAMPS AND CHIME CHIME ON, OFF

WINDSHIELD WIPER AJAR LAMP ON, OFF

BATTERY SAVER BATT SAVR ON, OFF

INTERIOR COURTESY LAMPS INT LAMPS ON, OFF

ONE TOUCH DOWN AND ACCESSORY DELAY ACCY RLY ON, OFF

ONE TOUCH DOWN AND ACCESSORY DELAY ONE TOUCH ON, OFF

4-WHEEL ELECTRONIC SHIFT CW/CCW ON, OFF

4-WHEEL ELECTRONIC SHIFT HIGH LAMP ON, OFF

4-WHEEL ELECTRONIC SHIFT LOW LAMP ON, OFF

4-WHEEL ELECTRONIC SHIFT AXLE ENGG ON, OFF

4-WHEEL ELECTRONIC SHIFT AXLE DSCN ON, OFF

4-WHEEL ELECTRONIC SHIFT PLATE PWR ON, OFF

4-WHEEL ELECTRONIC SHIFT SHFT CLCH ON, OFF

Symptom Chart

Condition Possible Sources Action

� The Vehicle Does Not Shift Between 2WD and 4WD Modes Properly � 4 WD mode switch. � Transfer case shift relays. � Contact plate A, B, C, or D. � Transfer case shift motor. � Circuitry. � Transfer case mechanism.

� GO to Pinpoint Test A.

� The Vehicle Does Not Shift Between 4WD High and 4WD Low Modes Properly � 4WD mode switch. � Neutral safety switch. � Brake pedal position (BPP)

switch.

� GO to Pinpoint Test B.



Pinpoint Tests

PINPOINT TEST A: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4WD MODES PROPERLY

� Transfer case mechanism. � Digital transmission range

(TR) sensor. � Circuitry.

� The Front Axle Is Not Engaging Properly (Transfer Case Motor Movement OK) � 4x4 solenoid. � 4x2 solenoid. � Vacuum motor. � Circuitry. � Vacuum lines. � Front differential

mechanism.

� GO to Pinpoint Test C.

� The 4x4 HIGH and/or 4x4 LOW Range Indicator Do/Does Not Operate Properly � Bulb. � Digital (TR). � Circuitry.

� GO to Pinpoint Test D.

� The 4x4 HIGH Does Not Engage at Speed Properly (Driveline Does Not Synchronize Properly) But Does Engage at Rest

� ESOF clutch relay. � Transfer case electric clutch. � Transfer case clutch

armature. � Hub release spring. � Circuitry.

� GO to Pinpoint Test E.

� No Communication With the Module — GEM � Fuse(s). � Circuitry. � GEM. � Fuse junction panel.

� GO to Pinpoint Test F.

CONDITIONS DETAILS/RESULTS/ACTIONS

A1 CHECK THE VOLTAGE OUTPUT FROM FUSE JUNCTION PANEL FUSE 15 (5A)

Measure the voltage between fuse junction panel fuse 15 (10A) pin 1 and ground.

� Is the voltage greater than 10 volts?

Yes GO to A4.

No GO to A2.

A2 CHECK FUSE JUNCTION PANEL FUSE 15 (5A) AND POWER DISTRIBUTION BOX FUSE 22 (50A)

Fuse 15 (10A)

Fuse 22 (50A)

� Are the fuses OK?

Yes GO to A3.



No REPLACE the fuse(s). CLEAR the DTCs. TEST the system for normal operation. If the fuse(s) fail again, CHECK for a short to ground. REPAIR as necessary.

A3 CHECK CIRCUIT 1052 (T/BK) FOR VOLTAGE

Fuse Junction Panel C243

Measure the voltage between fuse junction panel C243-11, circuit 1052 (T/BK), and ground.


Yes REPLACE the fuse junction panel. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR circuit 1052 (T/BK). CLEAR the DTCs. TEST the system for normal operation.

A4 CHECK THE IGNITION STATES — MONITOR THE GEM PID IGN_GEM

NGS

NOTE: If the vehicle is equipped with a manual transmission, depress the clutch pedal while turning the ignition switch to the START position.

Monitor the GEM PID IGN_GEM and rotate the ignition switch (11572) through the START, RUN, OFF, and ACC positions.

� Do the PID values agree with the ignition switch positions?

Yes GO to A5.

No REPAIR the ignition circuit(s) (RUN/ACC: circuit 297 [BK/LG], RUN: circuit 1040 [R/LB], START: circuit 32 [R/LB] or circuit 481 [GY/Y]) in question. CLEAR the DTCs. TEST the system for normal operation.

A5 RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCS)

Retrieve and Document Continuous DTCs

Clear Continuous DTCs

GEM On-Demand Self-Test

� Are any DTCs recorded?



Yes If DTC B1342, REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation. If DTC P1804, GO to Pinpoint Test D. If DTC P1806, GO to Pinpoint Test D. If DTC P1808, GO to Pinpoint Test D. If DTC P1810, GO to Pinpoint Test D. If DTC P1812, GO to A8 . If DTC P1815, GO to A8 . If DTC P1820, GO to A24 . If DTC P1822, GO to A24 . If DTC P1824, GO to Pinpoint Test E. If DTC P1826, GO to Pinpoint Test E. If DTC P1828, GO to A24 . If DTC P1830, GO to A24 . If DTC P1832, GO to Pinpoint Test C. If DTC P1834, GO to Pinpoint Test C. If DTC P1846, GO to A41 . If DTC P1850, GO to A41 . If DTC P1854, GO to A41 . If DTC P1858, GO to A41 . If DTC P1866, GO to A41 . If DTC P1867, GO to A41 . If DTC P1891, GO to A41 . If DTC P1876, GO to Pinpoint Test C. If DTC P1877, GO to Pinpoint Test C.

No GO to A6.

A6 CHECK THE HIGH LAMP INDICATOR — TRIGGER THE GEM ACTIVE COMMAND HIGH LAMP ON

Trigger the GEM active command HIGH LAMP to ON then OFF. The 4x4 indicator should illuminate and then turn off.

� Does the indicator illuminate correctly?

Yes GO to A7.

No GO to Pinpoint Test D.

A7 CHECK THE LOW LAMP INDICATOR — TRIGGER THE GEM ACTIVE COMMAND LOW LAMP ON

Trigger the GEM active command LOW LAMP to ON then OFF. The LOW indicator should illuminate and then turn off.


Yes GO to A8.


A8 CHECK THE 4WD MODE SWITCH — MONITOR THE GEM PID 4WDSGEM.



Monitor the GEM PID 4WDSGEM.

Place the mode switch in the 2H position.

� Does the GEM PID indicate 2WD?

Yes GO to A9.

No GO to A11.

A9 CHECK THE 4WD MODE SWITCH — MONITOR THE GEM PID 4WDSGEM (4H)


� Does the GEM PID indicate 4WDHGH?

Yes GO to A10.

No GO to A11.

A10 CHECK THE 4WD MODE SWITCH — MONITOR THE GEM PID 4WDSGEM (4L)

Place the mode switch in the 4L position.

� Does the GEM PID indicate 4WDLOW?

Yes GO to A20.

No GO to A11.

A11 CHECK THE 4WD MODE SWITCH — 2H



Mode Switch C230


Measure the resistance between the mode switch terminal 2 and terminal 3.

� Is the resistance between 3700 and 4100 ohms?

Yes GO to A12.

No REPLACE the mode switch; REFER to Section 308-07B. CLEAR the DTCs. TEST the system for normal operation.

A12 CHECK THE 4WD MODE SWITCH — 4H


Measure the resistance between the mode switch terminals 2 and 3.


Yes GO to A13.




A13 CHECK THE 4WD MODE SWITCH — 4L




Yes GO to A14.


A14 CHECK CIRCUIT 780 (DB) FOR OPEN

GEM C241

Measure the resistance between mode switch C230-3, circuit 780 (DB), and GEM C241-8, circuit 780 (DB).

� Is the resistance less than 5 ohms?

Yes GO to A15.

No REPAIR circuit 780 (DB). CLEAR the DTCs. TEST the system for normal operation.

A15 CHECK CIRCUIT 780 (DB) FOR SHORT TO GROUND

Measure the resistance between GEM C241-8, circuit 780 (DB), and ground.



� Is the resistance greater than 10,000 ohms?

Yes GO to A16.


A16 CHECK CIRCUIT 780 (DB) FOR SHORT TO POWER

Measure the voltage between GEM C241-8, circuit 780 (DB), and ground.

� Is any voltage indicated?

Yes REPAIR circuit 780 (DB). CLEAR the DTCs. TEST the system for normal operation.

No GO to A17.

A17 CHECK CIRCUIT 682 (DB) FOR OPEN

GEM C239



Yes GO to A18.



No REPLACE circuit 682 (DB). CLEAR the DTCs. TEST the system for normal operation.

A18 CHECK CIRCUIT 682 (DB) FOR SHORT TO GROUND

Multi-Function Switch C259

Measure the resistance between mode switch C230-2, circuit 682 (DB), and ground.


Yes GO to A19.


A19 CHECK CIRCUIT 682 (DB) FOR SHORT TO POWER

Measure the voltage between mode switch C230-2, circuit 682 (DB), and ground.



No REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation.

A20 CHECK THE FRONT AXLE ENGAGEMENT

Trigger the GEM active commands AXLE ENGG to ON and AXLE DSCN to OFF and drive a short distance.

Raise and support the vehicle with the engine running; refer to Section 100-02.

Spin one front tire. The other tire should spin in the opposite direction.



� Is the axle disconnect working properly?

Yes EXIT the active command mode; GO to A21 .

No GO to Pinpoint Test C.

A21 CHECK THE FRONT DRIVESHAFT ENGAGEMENT


Verify the front and rear driveshafts both spin.

� Is the transfer case locking the front driveshaft to the rear driveshaft?

Yes GO to A22.

No GO to A24.

A22 CHECK THE FRONT DRIVESHAFT DISENGAGEMENT

NOTE: When 4WD is disengaged, the front driveshaft may spin due to viscous drag in the transfer case, especially if cold. If this occurs, the front driveline can easily be stopped.

Place the mode switch in the 2H position. Only the rear driveshaft should spin.

� Does only the rear driveshaft spin?

Yes GO to A23.

No GO to A24.

A23 CHECK THE FRONT AXLE DISENGAGEMENT

Trigger the GEM active commands AXLE ENGG to OFF and AXLE DSCN to ON.

Spin one front tire and the other front tire should not spin.


Yes The 4WD system is working properly.




A24 CHECK THE TRANSFER CASE SHIFT RELAYS COIL ACTIVATION — MONITOR THE GEM PIDS MTR_CCW AND MTR_CW

Monitor the GEM PIDs MTR_CCW and MTR_CW while triggering the GEM active command CW/CCW ON.

� Do the GEM PIDs MTR_CCW and MTR_CW indicate ON---?

Yes GO to A25.

No If the GEM PID displays ON-B-, GO to A30 .

A25 CHECK THE TRANSFER CASE SHIFT RELAYS COIL DE-ACTIVATION — MONITOR THE GEM PIDS MTR_CCW AND MTR_CW

Monitor the GEM PIDS MTR_CCW and MTR_CW while triggering the GEM active command CW/CCW OFF.

� Do the GEM PIDs MTR_CCW and MTR_CW indicate OFF---?

Yes GO to A33.

No If the GEM PID displays OFFO-G, GO to A26 .

A26 CHECK THE VOLTAGE TO THE TRANSFER CASE SHIFT RELAYS COILS — CIRCUIT 704 (DG/LG)

Transfer Case Shift Relays C221

Measure the voltage between transfer case shift relays connector C221-5, circuit 704 (DG/LG), and ground.


Yes GO to A27.

No REPAIR circuit 704 (DG/LG). CLEAR the DTCs. TEST the system for normal operation.

A27 CHECK CIRCUIT 781 (O/LB) FOR OPEN

GEM C241

Measure the resistance between transfer case shift relays C221-9, circuit 781 (O/LB), and GEM C241-17, circuit 781 (O/LB).




Yes GO to A28.

No REPAIR circuit 781 (O/LB). CLEAR the DTCs. TEST the system for normal operation.

A28 CHECK CIRCUIT 782 (BR/W) FOR OPEN

Measure the resistance between transfer case shift relays C221-8, circuit 782 (BR/W), and GEM C241-16, circuit 782 (BR/W).


Yes GO to A29.

No REPAIR circuit 782 (BR/W). CLEAR the DTCs. TEST the system for normal operation.

A29 CHECK CIRCUITS 781 (O/LB) AND 782 (BR/W) FOR SHORT(S) TO GROUND

Measure the resistance between transfer case shift relays C221-8, circuit 782 (BR/W), and ground; and between transfer case shift relay C221-9, circuit 781 (O/LB), and ground.

� Are the resistances greater than 10,000 ohms?

Yes GO to A32.

No REPAIR circuit 781 (O/LB) and/or circuit 782 (BR/W). CLEAR the DTCs. TEST the system for normal operation.

A30 CHECK CIRCUIT 782 (BR/W) FOR SHORT TO POWER




GEM C241

Measure the voltage between transfer case shift relays C221-8, circuit 782 (BR/W), and ground.


Yes REPAIR circuit 782 (BR/W). CLEAR the DTCs. TEST the system for normal operation.

No GO to A31.

A31 CHECK CIRCUIT 781 (O/LB) FOR SHORT TO POWER

Measure the voltage between transfer case shift relays connector C221-9, circuit 781 (O/LB), and ground.


Yes REPAIR circuit 781 (O/LB). CLEAR the DTCs. TEST the system for normal operation.

No GO to A32.

A32 CHECK THE TRANSFER CASE SHIFT RELAYS COILS

Measure the resistance between the transfer case shift relays terminal 5 and terminals 8, 9.

� Are the resistances between 60 and 160 ohms?

Yes REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation.

No REPLACE the transfer case shift relays. CLEAR the DTCs. TEST the system for normal operation.



A33 CHECK THE VOLTAGE TO THE ELECTRIC SHIFT MOTOR — MOTOR ON

Transfer Case Assembly C201

Trigger the GEM active command CW/CCW to ON.

Measure the voltage between transfer case assembly C201-14, circuit 778 (O), and ground; and between transfer case assembly C201-15, circuit 777 (Y), and ground.

� Are the voltages greater than 10 volts?

Yes GO to A35.

No GO to A34.

A34 CHECK THE VOLTAGE TO THE TRANSFER CASE SHIFT RELAYS SWITCH — CIRCUIT 704 (DG/LG)


Measure the voltage between transfer case shift relays C221-3, circuit 704 (DG/LG), and ground.


Yes GO to A38.

No REPAIR circuit 704 (DG/LG). CLEAR the DTCs. TEST the system for normal operation.

A35 CHECK THE VOLTAGE TO THE ELECTRIC SHIFT MOTOR — MOTOR OFF



Trigger the GEM active command CW/CCW to OFF.



Yes GO to A36.

No GO to A37.

A36 CHECK CIRCUITS 777 (Y) AND 778 (O) FOR SHORT(S) TO POWER




Yes REPAIR circuit 778 (O) and/or circuit 777 (Y). CLEAR the DTCs. TEST the system for normal operation.

No REPLACE the transfer case shift relays. CLEAR the DTCs. TEST the system for normal operation.

A37 CHECK CIRCUITS 777 (Y) AND 778 (O)

Trigger the GEM active command CW/CCW to OFF.

Measure the resistance between transfer case assembly C201-14, circuit 778 (O), and ground; and between transfer case assembly C201-15, circuit 777 (Y), and ground.



� Are the resistances less than 5 ohms?

Yes RECONNECT the transfer case assembly. GO to A41 .

No GO to A40.

A38 CHECK CIRCUIT 777 (Y) FOR OPEN

Measure the resistance between transfer case shift relays C221-7, circuit 777 (Y), and transfer case assembly C201-15, circuit 777 (Y).


Yes GO to A39.

No REPAIR circuit 777 (Y). CLEAR the DTCs. TEST the system for normal operation.

A39 CHECK CIRCUIT 778 (O) FOR OPEN

Measure the resistance between transfer case shift relays C221-10, circuit 778 (O), and transfer case assembly C201-14, circuit 778 (O).


Yes REPLACE the transfer case shift relays. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR circuit 778 (O). CLEAR the DTCs. TEST the system for normal operation.

A40 CHECK THE GROUND TO THE TRANSFER CASE SHIFT RELAYS — CIRCUIT 57 (BK)




Measure the resistance between transfer case shift relays C221-1, circuit 57 (BK), and ground.


Yes REPLACE the transfer case shift relays. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR circuit 57 (BK). CLEAR the DTCs. TEST the system for normal operation.

A41 CHECK THE CONTACT PLATE SWITCHES

Monitor the GEM PIDs PLATE_A, PLATE_B, PLATE_C, and PLATE_D.

Place the mode switch in 2H and record the GEM PIDs.

Depress the brake pedal.

Place the mode switch in 4H and record the GEM PIDs.

Compare the PIDs with Table 4—Contact Plate Sensor Position Codes; refer to 4WD Tables.

� Do the GEM PIDs agree with Table 4?

Yes



REPAIR the transfer case (7A195) or shift motor assembly; REFER to Section 308-07B. CLEAR the DTCs. TEST the system for normal operation.

No GO to A42.

A42 MONITOR THE GEM PID PLATE_A FOR OPEN


Trigger the GEM active command PLATE POWER to ON.

Monitor the GEM PID PLATE_A.

� Does the GEM PID PLATE_A not indicate OPEN?

Yes GO to A44.

No GO to A43.

A43 CHECK THE CIRCUIT 771 (P/Y) TO THE CONTACT PLATE SWITCH A — MONITOR THE GEM PID PLATE_A

Connect a jumper wire between transfer case assembly C201-10, circuit 762 (Y/W), and C201-5, circuit 771 (P/Y).


� Does the GEM PID PLATE_A indicate CLOSED?

Yes REMOVE the jumper wire; GO to A49 .

No GO to A45.

A44 CHECK CIRCUIT 771 (P/Y) FOR SHORT TO GROUND



GEM C241

Measure the resistance between transfer case assembly C201-5, circuit 771 (P/Y), and ground.



No REPAIR circuit 771 (P/Y). CLEAR the DTCs. CYCLE the ignition OFF and then to RUN. TEST the system for normal operation.

A45 CHECK CIRCUIT 771 (P/Y) FOR OPEN

Measure the resistance between transfer case assembly C201-5, circuit 771 (P/Y), and GEM C241-21.


Yes GO to A46.

No REPAIR circuit 771 (P/Y). CLEAR the DTCs. TEST the system for normal operation.

A46 CHECK CIRCUIT 771 (P/Y) FOR SHORT TO POWER

GEM C241

Measure the voltage between transfer case assembly C201-5, circuit 771 (P/Y), and ground.




Yes REPAIR circuit 771 (P/Y). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

No GO to A47.

A47 CHECK CIRCUIT 762 (Y/W) FOR SHORT TO POWER

Measure the voltage between GEM C241-12, circuit 762 (Y/W), and ground.


Yes REPAIR circuit 762 (Y/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

No GO to A48.

A48 CHECK CIRCUIT 762 (Y/W) FOR OPEN

Measure the resistance between transfer case assembly C201-10, and GEM C241-12, circuit 762 (Y/W).



No REPAIR circuit 762 (Y/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

A49 MONITOR THE GEM PID PLATE_B FOR OPEN

Monitor the GEM PID PLATE_B.

� Does the GEM PID PLATE_B not indicate OPEN?



Yes GO to A51.

No GO to A50.

A50 CHECK THE CIRCUIT 770 (W) TO THE CONTACT PLATE SWITCH B — MONITOR THE GEM PID PLATE_B

Connect a jumper wire between transfer case assembly C201-10, circuit 762 (Y/W), and C201-1, circuit 770 (W).


� Does the GEM PID PLATE_B indicate CLOSED?


No GO to A52.

A51 CHECK CIRCUIT 770 (W) FOR SHORT TO GROUND

GEM C241

Measure the resistance between transfer case assembly C201-1, circuit 770 (W), and ground.



No REPAIR circuit 770 (W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

A52 CHECK CIRCUIT 770 (W) FOR OPEN

Measure the resistance between transfer case assembly C201-1, circuit 770 (W), and GEM C241-20, circuit 770 (W).




Yes GO to A53.


A53 CHECK CIRCUIT 770 (W) FOR SHORT TO POWER

Measure the voltage between transfer case assembly C201-1, circuit 770 (W), and ground.


Yes REPAIR circuit 770 (W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.


A54 MONITOR THE GEM PID PLATE_C FOR OPEN

Monitor the GEM PID PLATE_C.

� Does the GEM PID PLATE_C not indicate OPEN?

Yes GO to A56.

No GO to A55.

A55 CHECK THE CIRCUIT 764 (BR/W) TO THE CONTACT PLATE SWITCH C — MONITOR THE GEM PID PLATE_C

Connect a jumper wire between transfer case assembly C207-9, circuit 764 (BR/W), and C201-10, circuit 762 (Y/W).




� Does the GEM PID PLATE_C indicate CLOSED?


No GO to A57.

A56 CHECK CIRCUIT 764 (BR/W) FOR SHORT TO GROUND

GEM C241

Measure the resistance between transfer case assembly C201-9, circuit 764 (BR/W), and ground.



No REPAIR circuit 764 (BR/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

A57 CHECK CIRCUIT 764 (BR/W) FOR OPEN

Measure the resistance between transfer case assembly C201-9, circuit 764 (BR/W), and GEM C241-19, circuit 764 (BR/W).


Yes



GO to A58.


A58 CHECK CIRCUIT 764 (BR/W) FOR SHORT TO POWER

Measure the voltage between transfer case assembly C201-9, circuit 764 (BR/W), and ground.


Yes REPAIR circuit 764 (BR/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.


A59 MONITOR THE GEM PID PLATE_D FOR OPEN

Monitor the GEM PID PLATE_D.

� Does the GEM PID PLATE_D not indicate OPEN?

Yes GO to A61.

No GO to A60.

A60 CHECK CIRCUIT 763 (O/W) TO THE CONTACT PLATE SWITCH D — MONITOR THE GEM PID PLATE_D

Connect a jumper wire between transfer case assembly C201-10, circuit 762 (Y/W), and C201-13, circuit 763 (O/W).


� Does the PID PLATE_D indicate closed?

Yes REPLACE the transfer case shift motor (7G360); REFER to Section 308-07B. CLEAR the DTCs. TEST the system for normal operation.

No GO to A62.

A61 CHECK CIRCUIT 763 (O/W) FOR SHORT TO GROUND



GEM C241

Measure the resistance between transfer case assembly C201-13, circuit 763 (O/W), and ground.



No REPAIR circuit 763 (O/W). CLEAR the DTCs. CYCLE the ignition OFF and then to RUN. TEST the system for normal operation.

A62 CHECK CIRCUIT 763 (O/W) FOR OPEN

Measure the resistance between transfer case assembly C201-13, circuit 763 (O/W), and GEM C241-18, circuit 763 (O/W).


Yes GO to A63.

No REPAIR circuit 763 (O/W). CLEAR the DTCs. CYCLE the ignition OFF and then to RUN. TEST the system for normal operation.

A63 CHECK CIRCUIT 763 (O/W) FOR SHORT TO POWER

Measure the voltage between transfer case assembly C201-13, circuit 763 (O/W), and ground.




PINPOINT TEST B: THE VEHICLE DOES NOT SHIFT BETWEEN 4WD HIGH AND 4WD LOW MODES PROPERLY

Yes REPAIR circuit 763 (O/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.



B1 CHECK THE VOLTAGE OUTPUT FROM FUSE JUNCTION PANEL FUSE 15 (5A)

Measure the voltage between fuse 15 (5A) pin 1 and ground.


Yes GO to B4.

No GO to B2.

B2 CHECK FUSE JUNCTION PANEL FUSE 15 (5A) AND POWER DISTRIBUTION BOX FUSE 22 (50A)

Fuse 15 (5A)

Fuse 22 (50A)


Yes GO to B3.


B3 CHECK CIRCUIT 1052 (T/BK) FOR VOLTAGE








B4 CHECK THE IGNITION STATES — MONITOR THE GEM PID IGN_GEM

NGS

NOTE: If the vehicle is equipped with a manual transmission, depress the clutch pedal while turning the ignition switch to START.

Monitor the GEM PID IGN_GEM and rotate the ignition switch through the START, RUN, OFF, and ACC positions.


Yes GO to B5.

No REPAIR the ignition circuit(s) (RUN/ACC: circuit 297 [BK/LB], RUN: circuit 1040 [R/LB], START: circuit 32 [R/LB] or circuit 481 [GY/Y]) in question. CLEAR the DTCs. TEST the system for normal operation.

B5 RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCS)





Yes If DTC B1342, REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation. If DTC P0500, GO to B27 . If DTC P1483, GO to B20 . If DTC P1485, GO to B20 . If DTC P1804, GO to Pinpoint Test D. If DTC P1806, GO to Pinpoint Test D. If DTC P1808, GO to Pinpoint Test D. If DTC P1810, GO to Pinpoint Test D.



If DTC P1812, GO to B8 . If DTC P1815, GO to B8 . If DTC P1819, GO to B24 . If DTC P1820, GO to Pinpoint Test A. If DTC P1822, GO to Pinpoint Test A. If DTC P1824, GO to Pinpoint Test E. If DTC P1826, GO to Pinpoint Test E. If DTC P1828, GO to Pinpoint Test A. If DTC P1830, GO to Pinpoint Test A. If DTC P1832, GO to Pinpoint Test C. If DTC P1834, GO to Pinpoint Test C. If DTC P1846, GO to B31 . If DTC P1850, GO to B31 . If DTC P1854, GO to B31 . If DTC P1858, GO to B31 . If DTC P1866, GO to Pinpoint Test A. If DTC P1867, GO to Pinpoint Test A. If DTC P1876, GO to Pinpoint Test C. If DTC P1877, GO to Pinpoint Test C. If DTC P1891, GO to B31 .

No GO to B6.

B6 CHECK THE HIGH LAMP INDICATOR — TRIGGER THE GEM ACTIVE COMMAND HIGH LAMP ON

Trigger the GEM active command HIGH LAMP to ON, then OFF. The 4x4 indicator should illuminate, then turn off.


Yes GO to B7.


B7 CHECK THE LOW LAMP INDICATOR — TRIGGER THE GEM ACTIVE COMMAND LOW LAMP ON

Trigger the GEM active command LOW LAMP to ON, then OFF. The LOW indicator should illuminate, then turn off.


Yes GO to B8.


B8 CHECK THE 4WD MODE SWITCH — MONITOR THE GEM PID 4WDSGEM

Monitor the GEM PID 4WDSGEM.




� Does the GEM PID indicate 2WD?

Yes GO to B9.

No GO to B11.

B9 CHECK THE 4WD MODE SWITCH — MONITOR THE GEM PID 4WDSGEM (4H)


� Does the GEM PID indicate 4WDHGH?

Yes GO to B10.

No GO to B11.

B10 CHECK THE 4WD MODE SELECT SWITCH — MONITOR THE GEM PID 4WDSGEM (4L)


� Does the GEM PID indicate 4WDLOW?

Yes GO to B20.

No GO to B11.

B11 CHECK THE 4WD MODE SWITCH — 2H

Mode Switch C230




Measure the resistance between mode switch terminals 2 and 3.


Yes GO to B12.

No REPLACE the mode switch. REFER to Section 308-07B. CLEAR the DTCs. TEST the system for normal operation.

B12 CHECK THE 4WD MODE SWITCH — 4H




Yes GO to B13.


B13 CHECK THE 4WD MODE SELECT SWITCH — 4L






Yes GO to B14.


B14 CHECK CIRCUIT 780 (DB) FOR OPEN

GEM C241



Yes GO to B15.


B15 CHECK CIRCUIT 780 (DB) FOR SHORT TO GROUND





Yes GO to B16.


B16 CHECK CIRCUIT 780 (DB) FOR SHORT TO POWER




No GO to B17.

B17 CHECK CIRCUIT 682 (DB) FOR OPEN

GEM C239



Yes GO to B18.


B18 CHECK CIRCUIT 682 (DB) FOR SHORT TO GROUND





Yes GO to B19.


B19 CHECK CIRCUIT 682 (DB) FOR SHORT TO POWER





B20 CHECK BRAKE PEDAL POSITION (BPP) SWITCH INPUT — MONITOR THE GEM PID BOO_GEM

Monitor the GEM PID BOO_GEM.

Depress the brake pedal.

� Does the GEM PID BOO_GEM display ON?

Yes GO to B23.

No GO to B21.

B21 CHECK THE VOLTAGE TO THE BPP SWITCH — CIRCUIT 10 (LG/R)



BPP Switch C252

Measure the voltage between BPP switch C252, circuit 10 (LG/R), and ground.


Yes GO to B22.

No CHECK fuse junction panel 13 (15A). REPLACE if necessary. If fuse junction panel 13 (15A) is OK, REPAIR circuit 10 (LG/R). CLEAR the DTCs. TEST the system for normal operation.

B22 CHECK THE BPP SWITCH — MONITOR THE GEM PID BOO_GEM

Verify the GEM PID BOO_GEM displays OFF.

Connect a jumper wire between BPP switch C252, circuit 10 (LG/R), and circuit 511 (LG).

Monitor the GEM PID BOO_GEM.

� Does the GEM PID display ON?

Yes REPLACE the BPP switch; REFER to Section 417-01. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR circuit 511 (LG). TEST the system for normal operation. If the concern remains, REPLACE the GEM. REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation.

B23 CHECK THE CLUTCH INTERLOCK — MONITOR THE GEM PID CLTCHSW

Monitor the GEM PID CLTCHSW.

Verify the GEM PID CLTCHSW displays ACTIVE.



Verify the GEM PID CLTCHSW displays ACTIVE.

Verify that the GEM PID CLTCHSW indicates notACT when the transmission is in any position other than NEUTRAL or PARK.

� Do the GEM PIDs display correctly?

Yes GO to B24.

No DIAGNOSE the starter interrupt circuit and digital TR sensor; REFER to Section 303-06. If the circuits are OK, REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation.

B24 CHECK THE DIGITAL TR SENSOR — MONITOR THE GEM PID NTRL_SW

Monitor the GEM PID NTRL_SW.

Verify the GEM PID NTRL_SW displays NTRL.

Verify the GEM PID NTRL_SW displays notNTRL when the transmission is in any position other than NEUTRAL.

� Do the GEM PIDs indicate correctly?

Yes GO to B28.

No GO to B25.

B25 CHECK THE GROUND TO THE DIGITAL TRANSMISSION RANGE (DTR) SENSOR

Digital TR Sensor C182

Measure the resistance between digital TR sensor C182-7, circuit 57 (BK), and ground.


Yes GO to B26.

No REPAIR circuit 57 (BK). CLEAR the DTCs. TEST the system for normal operation.

B26 CHECK THE DIGITAL TR SENSOR — MONITOR THE GEM PID NTRL_SW

Monitor the GEM PID NTRL_SW.



Verify the GEM PID NTRL_SW displays notNTRL.

Connect a jumper wire between digital TR sensor C182-7, circuit 57 (BK), and C182-8, circuit 463 (R/W).

� Does the GEM PID NTRL_SW indicate NTRL?

Yes REPLACE the digital TR sensor; REFER to Section 307-01A or Section 307-01B. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR circuit 463 (R/W). CLEAR the DTCs. TEST the system for normal operation. If the concern remains, REPLACE the GEM. REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation.

B27 CHECK THE VEHICLE SPEED SENSOR (VSS) — MONITOR THE GEM PID VSS_GEM

Monitor the GEM PID VSS_GEM while driving the vehicle from 0 to 88.5 km/h (55 mph).

� Does the GEM PID VSS_GEM agree with the speedometer?

Yes GO to B30.

No GO to B28.

B28 CHECK CIRCUIT 676 (PK/O) FOR OPEN

VSS C186


Measure the resistance between VSS C186, circuit 676 (PK/O), and fuse junction panel C242-9, circuit 676 (PK/O).




Yes GO to B29.

No REPAIR circuit 676 (PK/O). CLEAR the DTCs. TEST the system for normal operation.

B29 CHECK CIRCUIT 679 (GY/BK) FOR OPEN


Measure the resistance between VSS C186, circuit 679 (GY/BK), and fuse junction panel C243-21, circuit 679 (GY/BK).


Yes GO to B30.

No REPAIR circuit 679 (GY/BK). CLEAR the DTCs. TEST the system for normal operation.

B30 CHECK THE CIRCUITS BETWEEN THE GEM AND THE FUSE JUNCTION PANEL

GEM C267

Measure the resistance between fuse junction panel C242 terminal 9 and fuse junction panel C267 terminal 10; and between fuse junction panel C243 terminal 21 and GEM C267 terminal 18.


Yes



REPLACE the vehicle speed sensor; REFER to Section 303-14. CLEAR the DTCs. TEST the system for normal operation.

No REPLACE the fuse junction panel. CLEAR the DTCs. TEST the system for normal operation.

B31 CHECK THE CONTACT PLATE SWITCHES — MONITOR THE GEM PIDS PLATE_A, PLATE_B, PLATE_C, AND PLATE_D

Monitor GEM PIDs PLATE_A, PLATE_B, PLATE_C, and PLATE_D.

Place the mode switch in the 4H position and record the PIDs.

Place the mode switch in the 4L position and record the PIDs.

Compare the GEM PIDs with Table 4—Contact Plate Sensor Position Codes; refer to 4WD Tables.

� Do the GEM PIDs agree with Table 4?

Yes REPAIR the transfer case or shift motor assembly. REFER to Section 308-07B. CLEAR the DTCs. TEST the system for normal operation.

No GO to B32.

B32 MONITOR THE GEM PID PLATE_A FOR OPEN


Trigger the GEM active command PLATE POWER to ON.




� Does the GEM PID PLATE_A not indicate OPEN?

Yes GO to B34.

No GO to B33.

B33 CHECK CIRCUIT 771 (P/Y) TO THE CONTACT PLATE SWITCH A — MONITOR THE GEM PID PLATE_A

Connect a jumper wire between transfer case assembly C201-5, circuit 771 (P/Y), and C201-10, circuit 762 (Y/W).


� Does the GEM PID PLATE_A indicate CLOSED?

Yes REMOVE the jumper wire; GO to B39 .

No GO to B35.

B34 CHECK CIRCUIT 771 (P/Y) FOR SHORT TO GROUND

Measure the resistance between GEM C241-21, circuit 771 (P/Y), and ground.



No REPAIR circuit 771 (P/Y). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

B35 CHECK CIRCUIT 771 (P/Y) FOR OPEN

GEM C241

Measure the resistance between transfer case assembly C201-5, circuit 771 (P/Y), and GEM C241-21, circuit 771 (P/Y).




Yes GO to B36.

No REPAIR circuit 771 (P/Y). CLEAR the DTCs. TEST the system for normal operation.

B36 CHECK CIRCUIT 771 (P/Y) FOR SHORT TO POWER

Measure the voltage between transfer case assembly C201-5, circuit 771 (P/Y), and ground.


Yes REPAIR circuit 771 (P/Y). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

No GO to B37.

B37 CHECK CIRCUIT 762 (Y/W) FOR SHORT TO POWER

Measure the voltage between GEM C241-12, circuit 762 (Y/W), and ground.


Yes REPAIR circuit 762 (Y/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

No GO to B38.

B38 CHECK CIRCUIT 762 (Y/W) FOR OPEN

Measure the resistance between GEM C241-12, circuit 762 (Y/W), and transfer case assembly C201-10, circuit 762 (Y/W).




Yes GO to B39.

No REPAIR circuit 762 (Y/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

B39 MONITOR THE GEM PID PLATE_B FOR OPEN


� Does the GEM PID PLATE_B not indicate OPEN?

Yes GO to B41.

No GO to B40.

B40 CHECK CIRCUIT 770 (W) TO THE CONTACT PLATE SWITCH B — MONITOR THE GEM PID PLATE_B

Connect a jumper wire between transfer case assembly C201-1, circuit 770 (W), and C201-10, circuit 762 (Y/W).


� Does the GEM PID PLATE_B indicate CLOSED?


No GO to B42.

B41 CHECK CIRCUIT 770 (W) FOR SHORT TO GROUND

GEM C241

Measure the resistance between GEM C241-20, circuit 770 (W), and ground.






B42 CHECK CIRCUIT 770 (W) FOR OPEN

GEM C241

Measure the resistance between transfer case assembly C201-1, circuit 770 (W), and GEM C241-20, circuit 770 (W).


Yes GO to B43.


B43 CHECK CIRCUIT 770 (W) FOR SHORT TO POWER

Measure the voltage between transfer case assembly C201-1, circuit 770 (W), and ground.




Yes REPAIR circuit 770 (W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.


B44 MONITOR THE GEM PID PLATE_C FOR OPEN


� Does the GEM PID PLATE_C not indicate OPEN?

Yes GO to B46.

No GO to B45.

B45 CHECK CIRCUIT 764 (BR/W) TO THE CONTACT PLATE SWITCH C — MONITOR THE GEM PID PLATE_C

Connect a jumper wire between transfer case assembly C201-9, circuit 764 (BR/W), and C201-10, circuit 762 (Y/W).


� Does the GEM PID PLATE_C indicate CLOSED?


No GO to B47.

B46 CHECK CIRCUIT 764 (BR/W) FOR SHORT TO GROUND

GEM C241

Measure the resistance between GEM C241-19, circuit 764 (BR/W), and ground.


Yes REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for



normal operation.

No REPAIR circuit 764 (BR/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

B47 CHECK CIRCUIT 764 (BR/W) FOR OPEN

GEM C241

Measure the resistance between transfer case assembly C201-9, circuit 764 (BR/W), and GEM C241-19, circuit 764 (BR/W).


Yes GO to B48.


B48 CHECK CIRCUIT 764 (BR/W) FOR SHORT TO POWER

Measure the voltage between transfer case assembly C201-9, circuit 764 (BR/W), and ground.


Yes REPAIR circuit 764 (BR/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.


B49 MONITOR THE GEM PID PLATE_D FOR OPEN


� Does the GEM PID PLATE_D not indicate OPEN?

Yes GO to B51.



No GO to B50.

B50 CHECK CIRCUIT 763 (O/W) TO THE CONTACT PLATE SWITCH D — MONITOR THE GEM PID PLATE_D

Connect a jumper wire between transfer case assembly C201-10, circuit 762 (Y/W), and C201-13, circuit 763 (O/W).


� Does the GEM PID PLATE_D indicate CLOSED?

Yes REPLACE the transfer case shift motor; REFER to Section 308-07B. CLEAR the DTCs. TEST the system for normal operation.

No GO to B52.

B51 CHECK CIRCUIT 763 (O/W) FOR SHORT TO GROUND

GEM C241

Measure the resistance between GEM C241-18, circuit 763 (O/W), and ground.



No REPAIR circuit 763 (O/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.

B52 CHECK CIRCUIT 763 (O/W) FOR OPEN

GEM C241



PINPOINT TEST C: THE FRONT AXLE IS NOT ENGAGING PROPERLY (TRANSFER CASE MOTOR MOVEMENT OK)

Measure the resistance between transfer case assembly C201-9, circuit 763 (O/W), and GEM C241-18, circuit 763 (O/W).


Yes GO to B53.

No REPAIR circuit 763 (O/W). CLEAR the DTCs. TEST the system for normal operation.

B53 CHECK CIRCUIT 763 (O/W) FOR SHORT TO POWER

Measure the voltage between transfer case assembly C201-13, circuit 763 (O/W), and ground.


Yes REPAIR circuit 763 (O/W). CLEAR the DTCs. CYCLE the ignition OFF then ON. TEST the system for normal operation.



C1 CHECK THE VOLTAGE OUTPUT FROM FUSE JUNCTION PANEL FUSE 15 (5A)

Measure the voltage between fuse junction panel fuse 15 (5A) pin 1, and ground.




Yes GO to C4.

No GO to C2.

C2 CHECK FUSE JUNCTION PANEL FUSE 15 (5A) AND POWER DISTRIBUTION BOX FUSE 22 (50A)

Fuse 15 (5A)

Fuse 22 (50A)


Yes GO to C3.


C3 CHECK CIRCUIT 1052 (T/BK) FOR VOLTAGE


Measure the voltage between fuse junction panel C243-11, 1052 (T/BK), and ground.




C4 CHECK THE IGNITION STATES — MONITOR THE GEM PID IGN_GEM

NGS



� Do the GEM PID values agree with the ignition switch positions?

Yes GO to C5.

No



REPAIR ignition circuit(s) (RUN/ACC: circuit 297 [BK/LB], RUN: circuit 1040 [R/LB], START: circuit 32 [R/LB] or circuit 481 [GY/Y] in question. CLEAR the DTCs. TEST the system for normal operation.

C5 RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCS)




� Are any DTCs recorded

Yes If DTC B1342, REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation. If DTC P1804, GO to Pinpoint Test D. If DTC P1806, GO to Pinpoint Test D. If DTC P1808, GO to Pinpoint Test D. If DTC P1810, GO to Pinpoint Test D. If DTC P1812, GO to Pinpoint Test A. If DTC P1815, GO to Pinpoint Test A. If DTC P1820, GO to Pinpoint Test A. If DTC P1822, GO to Pinpoint Test A. If DTC P1824, GO to Pinpoint Test E. If DTC P1826, GO to Pinpoint Test E. If DTC P1828, GO to Pinpoint Test A. If DTC P1830, GO to Pinpoint Test A. If DTC P1832, GO to C12 . If DTC P1834, GO to C12 . If DTC P1838, GO to Pinpoint Test A. If DTC P1846, GO to Pinpoint Test A or B. If DTC P1850, GO to Pinpoint Test A or B. If DTC P1854, GO to Pinpoint Test A or B. If DTC P1858, GO to Pinpoint Test A or B. If DTC P1876, GO to C12 . If DTC P1877, GO to C12 . If DTC P1891, GO to Pinpoint Test A or B.

No GO to C6.

C6 CHECK THE HIGH LAMP INDICATOR — TRIGGER THE GEM ACTIVE COMMAND HIGH LAMP ON

Trigger the GEM active command HIGH LAMP to ON, then OFF. The 4x4 indicator should illuminate, then turn off.




Yes GO to C7.


C7 CHECK THE LOW LAMP INDICATOR — TRIGGER THE GEM ACTIVE COMMAND LOW LAMP ON

Trigger the GEM active command LOW LAMP to ON, then OFF. The LOW indicator should illuminate, then turn off.


Yes GO to C8.


C8 CHECK THE FRONT AXLE ENGAGEMENT

Trigger the GEM active commands AXLE ENGG to ON and AXLE DSCN to OFF.


Spin one front tire. The other front tire should spin in the opposite direction.


Yes EXIT the active command modes. LOWER the vehicle. GO to C9 .

No GO to C12.

C9 CHECK THE FRONT DRIVESHAFT ENGAGEMENT

Place the mode switch in the 4H position and drive a short distance.


The front and rear driveshafts should both spin.

� Is the transfer case locking the front driveshaft to the rear driveshaft?

Yes GO to C10.

No GO to Pinpoint Test A.



C10 CHECK THE FRONT DRIVESHAFT DISENGAGEMENT

NOTE: When 4WD is disengaged, the front driveshaft may spin due to viscous drag in the transfer case, especially if cold. If this occurs, the front driveline can easily be stopped.

Disengage 4WD. Only the rear driveshaft should spin.

� Does only the rear driveshaft spin?

Yes GO to C11.

No GO to Pinpoint Test A.

C11 CHECK THE FRONT AXLE AND THE FRONT DRIVESHAFT DISENGAGEMENT


Spin one front tire. The other front tire should not spin.


Yes The 4WD system is working properly.

No GO to C12.

C12 CHECK 4WD AND 2WD VACUUM HUB SOLENOID CIRCUITS — MONITOR THE GEM PIDS 4WDSOL AND 2WDSOL

Monitor the GEM PIDs 4WDSOL and 2WDSOL while triggering the GEM active commands AXLE ENGG and AXLE DSCN to ON.

� Does the GEM PID 4WDSOL indicate ON--- and the GEM PID 2WDSOL indicate ON---?

Yes GO to C13.

No If PID displays ON-B-, GO to C14 .

C13 CHECK 4WD AND 2WD VACUUM SOLENOIDS — MONITOR THE GEM PIDS 4WDSOL AND 2WDSOL

Monitor the GEM PIDs 4WDSOL and 2WDSOL while triggering the GEM active commands AXLE ENGG and AXLE DSCN to OFF.

� Does the GEM PID 4WDSOL indicate OFF--- and GEM PID 2WDSOL indicate OFF---?

Yes GO to C23.

No If the GEM PIDs display OFFO-G, GO to C16 .

C14 CHECK CIRCUITS 145 (GY/BK) AND 605 (R) FOR SHORT TO POWER



4WD Vacuum Solenoid C180


GEM C241

Measure the voltage between 4WD vacuum solenoid C180, circuit 605 (R), and ground; and between 2WD vacuum solenoid C181, circuit 145 (GY/BK), and ground.


Yes REPAIR the circuit(s) in question. CLEAR the DTCs. TEST the system for normal operation.

No RECONNECT GEM C241, 4WD vacuum solenoid and 2WD vacuum solenoid. GO to C15 .

C15 RECHECK THE 4WD AND 2WD VACUUM SOLENOIDS — MONITOR THE GEM PIDS 4WDSOL AND 2WDSOL

Monitor the GEM PIDS 4WDSOL and 2WDSOL while triggering the GEM active commands AXLE ENGG and AXLE DSCN to ON.

� Do the GEM PIDS 4WDSOL and 2WDSOL indicate ON-B-?


No REPLACE the vacuum solenoid that displays ON-B-. CLEAR the DTCs. TEST the system for normal operation.

C16 CHECK THE VOLTAGE TO THE 4WD AND 2WD VACUUM SOLENOIDS — CIRCUIT 294 (W/LB)





Measure the voltage between 4WD vacuum solenoid C180, circuit 294 (W/LB), and ground; and between 2WD vacuum solenoid C181, circuit 294 (W/LB), and ground.


Yes GO to C17.

No REPAIR circuit 294 (W/LB) or REPLACE fuse junction panel fuse 23 (10A). CLEAR the DTCs. TEST the system for normal operation.

C17 CHECK THE 4WD VACUUM SOLENOID FOR CONTINUITY

Measure the resistance between 4WD vacuum solenoid terminals 1 and 2.


Yes GO to C18.

No REPLACE the 4WD vacuum solenoid. CLEAR the DTCs. TEST the system for normal operation.

C18 CHECK THE 2WD VACUUM SOLENOID FOR CONTINUITY

Measure the resistance between 2WD vacuum solenoid terminals 1 and 2.


Yes GO to C19.

No



REPLACE the 2WD vacuum solenoid. CLEAR the DTCs. TEST the system for normal operation.

C19 CHECK CIRCUIT 145 (GY/BK) FOR OPEN

GEM C241

Measure the resistance between GEM C241-2, circuit 145 (GY/BK), and 2WD vacuum solenoid C181, circuit 145 (GY/BK).


Yes GO to C20.


C20 CHECK CIRCUIT 605 (R) FOR OPEN

Measure the resistance between GEM C241-7, circuit 605 (R), and 4WD vacuum solenoid C180, circuit 605 (R).


Yes GO to C21.

No REPAIR circuit 605 (R). CLEAR the DTCs. TEST the system for normal operation.

C21 CHECK CIRCUIT 145 (GY/BK) FOR SHORT TO GROUND

Measure the resistance between GEM C241-2, circuit 145 (GY/BK), and ground.


Yes GO to C22.


C22 CHECK CIRCUIT 605 (R) FOR SHORT TO GROUND

Measure the resistance between GEM C241-7, circuit 605 (R), and ground.





No REPAIR circuit 605 (R). CLEAR the DTCs. TEST the system for normal operation.

C23 CHECK THE VACUUM AT THE 4WD AND 2WD VACUUM SOLENOIDS

Verify the vacuum (with the engine running) at the feed lines on the 2WD and 4WD vacuum solenoids.

� Is approximately 10 in Hg (25A cm Hg) of vacuum present?

Yes GO to C24.

No REPAIR the vacuum feed line in question. CLEAR the DTCs. TEST the system for normal operation.

C24 CHECK THE 4WD AND 2WD VACUUM SOLENOIDS — CLOSED

Connect Vacuum Pump to the feed line of the vacuum solenoid being tested.

Monitor the GEM PIDs 2WDSOL and 4WDSOL while triggering the GEM active commands AXLE ENGG and AXLE DSCN to OFF.

Apply vacuum and verify the vacuum solenoids are closed.

� Are the solenoids closed?

Yes RELEASE the applied vacuum. GO to C25 .

No REPLACE the vacuum solenoid in question. CLEAR the DTCs. TEST the system for normal operation.

C25 CHECK THE 4WD AND 2WD VACUUM SOLENOIDS — OPEN



PINPOINT TEST D: THE 4X4 HIGH AND/OR 4X4 LOW RANGE INDICATOR DO/DOES NOT OPERATE PROPERLY

Trigger the GEM active commands AXLE ENGG and AXLE DSCN to ON.

Apply vacuum and verify that the vacuum solenoids are open.

� Are the solenoids open?

Yes RELEASE the applied vacuum. GO to C26 .

No REPLACE the vacuum solenoid(s) in question. CLEAR the DTCs. TEST the system for normal operation.

C26 CHECK THE VACUUM FEED LINES TO THE VACUUM MOTOR

Verify that the feed lines from the vacuum solenoids to the vacuum motor are OK.

� Are the feed lines OK?

Yes RECONNECT the vacuum lines; GO to C27 .

No REPAIR the feed line(s) in question. CLEAR the DTCs. TEST the system for normal operation.

C27 CHECK THE VACUUM MOTOR

Remove the linkage from the vacuum motor.

Trigger the GEM active commands AXLE ENGG to ON and AXLE DSCN to OFF.

� Does the vacuum motor move to the engaged position?

Yes REPAIR the center disconnect assembly; REFER to Section 205-03. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR the vacuum motor. CLEAR the DTCs. TEST the system for normal operation.


D1 CHECK THE VOLTAGE OUTPUT FROM FUSE JUNCTION PANEL FUSE 15 (5A)

Measure the voltage between fuse junction panel fuse 15 (5A) pin 1, and ground.


Yes GO to D4.



No GO to D2.

D2 CHECK FUSE JUNCTION PANEL FUSE 15 (5A) AND POWER DISTRIBUTION BOX FUSE 22 (50A)

Fuse 15 (5A)

Fuse 22 (50A)


Yes GO to D3.

No REPLACE the fuse(s). CLEAR the DTCs. TEST the system for normal operation. If the fuse(s) fails again, CHECK for a short to ground. REPAIR as necessary.

D3 CHECK CIRCUIT 1052 (T/BK) FOR VOLTAGE


Measure the voltage between fuse junction panel C243-11, 1052 (T/BK), and ground.




D4 CHECK THE IGNITION STATES — MONITOR THE GEM PID IGN_GEM

NGS




Yes GO to D5.

No REPAIR ignition circuit(s) (RUN/ACC: circuit 297 [BK/LB], RUN: circuit 1040 [R/LB], START: circuit 32 [R/LB] or circuit 481 [GY/Y] in question. CLEAR the DTCs. TEST the system for normal operation.

D5 RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCS)







Yes If DTC B1342, REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation. If DTC P1804, GO to D6 . If DTC P1806, GO to D6 . If DTC P1808, GO to D6 . If DTC P1810, GO to D6 . If DTC P1812, GO to Pinpoint Test A. If DTC P1815, GO to Pinpoint Test A. If DTC P1820, GO to Pinpoint Test A. If DTC P1822, GO to Pinpoint Test A. If DTC P1824, GO to Pinpoint Test E. If DTC P1826, GO to Pinpoint Test E. If DTC P1828, GO to Pinpoint Test A. If DTC P1830, GO to Pinpoint Test A. If DTC P1832, GO to Pinpoint Test C. If DTC P1834, GO to Pinpoint Test C. If DTC P1838, GO to Pinpoint Test A. If DTC P1846, GO to Pinpoint Test A or B. If DTC P1850, GO to Pinpoint Test A or B. If DTC P1854, GO to Pinpoint Test A or B. If DTC P1858, GO to Pinpoint Test A or B. If DTC P1876, GO to Pinpoint Test C. If DTC P1877, GO to Pinpoint Test C. If DTC P1891, GO to Pinpoint Test A or B.

No GO to D6.

D6 CHECK THE INDICATORS — MONITOR THE GEM PIDS 4WDHIGH AND 4WDLOW

Monitor the GEM PIDs 4WDHIGH and 4WDLOW while triggering the GEM active commands HIGH LAMP and LOW LAMP to ON, then OFF. The 4x4 and LOW RANGE indicators should illuminate, then turn off.

� Does the PID display ON-B-?

Yes GO to D9.



No If the PID displays OFFO-G and lamp stays on continuously, GO to D7 . If the PID displays OFFO-G and the lamp does not illuminate, REFER to Section 413-01A.

D7 CHECK THE GEM FOR SHORT TO GROUND

GEM C241

� Is the lamp still illuminated?

Yes GO to D8.


D8 CHECK CIRCUITS 210 (LB) AND 975 (BR/Y) FOR SHORT TO GROUND

Instrument Cluster C236

Measure the resistance between:

� 4x4 HIGH: GEM C241-9, circuit 210 (LB), and ground.

� 4x4 LOW: GEM C241-10, circuit 975 (BR/Y), and ground.

� Are the resistances greater than 10,000 ohms?

Yes REPAIR the instrument cluster. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR circuit 210 (LB) and/or 975 (BR/Y). CLEAR the DTCs. TEST the system for normal operation.

D9 CHECK CIRCUITS 210 (LB) AND 975 (BR/Y) FOR SHORT TO POWER

Instrument Cluster C236



PINPOINT TEST E: THE 4X4 HIGH DOES NOT ENGAGE AT SPEED PROPERLY (DRIVELINE DOES NOT SYNCHRONIZE PROPERLY) BUT DOES ENGAGE AT REST

GEM C241

Measure the voltage between:

� 4x4 HIGH: GEM C241-9, circuit 210 (LB), and ground.

� 4x4 LOW: GEM C241-10, circuit 975 (BR/Y), and ground.


Yes REPAIR circuit 210 (LB) and/or 975 (BR/Y). CLEAR the DTCs. TEST the system for normal operation.

No GO to D10.

D10 CHECK INSTRUMENT CLUSTER FOR SHORT TO POWER — MONITOR THE GEM PIDS 4WDHIGH AND 4WDLOW

Monitor the GEM PIDs 4WDHIGH and/or 4WDLOW while triggering the GEM active commands HIGH LAMP and LOW LAMP to ON.

� Does the PID indicate ON-B-?


No REPAIR the instrument cluster; REFER to Section 413-01A. CLEAR the DTCs. TEST the system for normal operation.


E1 RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCS)

NGS







Yes If DTC B1342, REPLACE the GEM; REFER to Section 419-10. CLEAR the DTCs. TEST the system for normal operation. If DTC P1804, GO to Pinpoint Test D. If DTC P1806, GO to Pinpoint Test D. If DTC P1808, GO to Pinpoint Test D. If DTC P1810, GO to Pinpoint Test D. If DTC P1812, GO to Pinpoint Test A. If DTC P1815, GO to Pinpoint Test A. If DTC P1820, GO to Pinpoint Test A. If DTC P1822, GO to Pinpoint Test A. If DTC P1824, GO to E4 . If DTC P1826, GO to E4 . If DTC P1828, GO to Pinpoint Test A. If DTC P1830, GO to Pinpoint Test A. If DTC P1832, GO to Pinpoint Test C. If DTC P1834, GO to Pinpoint Test C. If DTC P1838, GO to Pinpoint Test A. If DTC P1846, GO to Pinpoint Test A or B. If DTC P1850, GO to Pinpoint Test A or B. If DTC P1854, GO to Pinpoint Test A or B. If DTC P1858, GO to Pinpoint Test A or B. If DTC P1876, GO to Pinpoint Test C. If DTC P1877, GO to Pinpoint Test C. If DTC P1891, GO to Pinpoint Test A or B.

No GO to E2.

E2 CHECK THE FRONT AXLE ENGAGEMENT

Trigger the GEM active commands AXLE ENGG to ON and AXLE DSCN to OFF and drive a short distance.


Spin one front tire. The other tire should spin in the opposite direction.


Yes Exit the GEM active command modes; GO to E3 .


E3 CHECK THE FRONT AXLE DISENGAGEMENT




Spin one front tire and the other front tire should not spin.


Yes The 4x4 system is working properly.


E4 CHECK THE ESOF CLUTCH RELAY COIL CIRCUIT — ENERGIZED

Monitor the GEM PID 4WDELCL while triggering the GEM active command SHFT CLCH to ON.

� Does the GEM PID 4WDELCL indicate ON---?

Yes GO to E7.

No If the PID displays ON-B-, GO to E5 .

E5 CHECK THE ESOF CLUTCH RELAY

ESOF Clutch Relay

Check the ESOF clutch relay, refer to Component Test.

� Is the ESOF clutch relay OK?

Yes GO to E6.

No REPLACE the ESOF clutch relay. CLEAR the DTCs. TEST the system for normal operation.

E6 CHECK CIRCUIT 976 (O) FOR SHORT TO POWER

GEM C241

Measure the voltage between ESOF clutch relay connector pin 2, circuit 976 (O), and ground.




Yes REPAIR circuit 976 (O). CLEAR the DTCs. TEST the system for normal operation.


E7 CHECK THE ESOF CLUTCH RELAY COIL CIRCUIT — DE-ENERGIZED

Monitor the GEM PID 4WDELCL while triggering the GEM active command SHFT CLCH to OFF.

� Does the GEM PID 4WDELCL indicate OFF---?

Yes GO to E12.

No If the PID displays OFFO-G, GO to E8 .

E8 CHECK THE VOLTAGE TO THE ESOF CLUTCH RELAY COIL — CIRCUIT 294 (W/LB)

ESOF Clutch Relay

Measure the voltage between ESOF clutch relay connector pin 1, circuit 294 (W/LB), and ground.


Yes GO to E9.

No CHECK fuse junction panel fuse 23 (10A). REPLACE if necessary. If OK, REPAIR circuit 294 (W/LB). CLEAR the DTCs. TEST the system for normal operation.



E9 CHECK THE ESOF CLUTCH RELAY

Check the ESOF clutch relay; refer to Component Test.

� Is the ESOF clutch relay OK?

Yes GO to E10.


E10 CHECK CIRCUIT 976 (O) FOR SHORT TO GROUND

GEM C241

Measure the resistance between ESOF clutch relay connector pin 2, circuit 976 (O), and ground.


Yes GO to E11.


E11 CHECK CIRCUIT 976 (O) FOR OPEN

Measure the resistance between ESOF clutch relay connector pin 2, circuit 976 (O), and GEM C241-14, circuit 976 (O).




E12 CHECK CIRCUIT 779 (BR) FOR VOLTAGE — ENERGIZED




Trigger the GEM active command SHFT CLCH to ON.

Measure the voltage between transfer case assembly C201-16, circuit 779 (BR), and ground.


Yes GO to E13.

No GO to E15.

E13 CHECK CIRCUIT 779 (BR) FOR VOLTAGE — DE-ENERGIZED


Trigger the GEM active command SHFT CLCH to OFF.

Measure the voltage between transfer case assembly C201-16, circuit 779 (BR), and ground.

� Is the voltage 0 volts?

Yes GO to E17.

No GO to E14.

E14 CHECK CIRCUIT 779 (BR) FOR SHORT TO POWER



ESOF Clutch Relay


Measure the voltage between ESOF clutch relay connector pin 5, circuit 779 (BR), and ground.


Yes REPAIR circuit 779 (BR). CLEAR the DTCs. TEST the system for normal operation.


E15 CHECK CIRCUIT 704 (DG/LG) FOR VOLTAGE

ESOF Clutch Relay

Measure the voltage between ESOF clutch relay connector pin 3, circuit 704 (DG/LG), and ground.


Yes GO to E16.

No CHECK power distribution box fuse 17 (30A). REPLACE if necessary. If OK, REPAIR circuit 704 (DG/LG). TEST the system for normal operation.

E16 CHECK CIRCUIT 779 (BR) FOR OPEN

Measure the resistance between ESOF clutch relay connector pin 5, circuit 779 (BR), and transfer case C201-16, circuit 779 (BR).



PINPOINT TEST F: NO COMMUNICATION WITH THE MODULE — GEM


Yes REPLACE the ESOF clutch relay. CLEAR the DTCs. TEST the system for normal operation.

No REPAIR circuit 779 (BR). CLEAR the DTCs. TEST the system for normal operation.

E17 CHECK THE TRANSFER CASE SYNCHRONIZATION

Raise and support the vehicle.

WARNING: The front driveshaft must be removed to prevent possible damage to the front axle.

Remove the front driveshaft; refer to Section 205-01.


Rotate the tires between 20 and 25 mph (32-40 kph) and shift into 4H.

� Does the front output of the transfer case rotate?

Yes VERIFY the transfer case concern; REFER to Symptom Chart.

No REFER to Section 308-07B.


F1 CHECK THE IGNITION STATES — MONITOR THE GEM PID IGN_GEM

NGS

NOTE: If the vehicle is equipped with a manual transmission, depress the clutch pedal when



turning the ignition switch to START.

Monitor the GEM PID IGN_GEM while turning the ignition switch through the START, RUN, OFF, and ACC positions.


Yes GO to F2.

No REPAIR the ignition circuit (RUN/ACC: circuit 297 [BK/LG], RUN: circuit 1040 [R/LB], START: circuit 32 [R/LB] or circuit 481 [GY/Y] in question. CLEAR the DTCs. TEST the system for normal operation.

F2 CHECK FUSE JUNCTION PANEL FUSE 15 (5A) AND POWER DISTRIBUTION BOX FUSE 22 (50A)

Fuse 15 (5A)

Fuse 22 (50A)


Yes GO to F3.

No GO to F5.

F3 CHECK CIRCUIT 1052 (T/BK) FOR VOLTAGE




Yes GO to F4.


F4 CHECK FUSE JUNCTION PANEL FOR VOLTAGE



GEM C267


Measure the voltage between fuse junction panel C267 terminal 4, and ground; and between fuse junction panel C267 terminal 16, and ground.


Yes GO to F8.


F5 CHECK FUSE JUNCTION PANEL FUSE 15 (5A) AND POWER DISTRIBUTION BOX FUSE 22 (50A) — GEM DISCONNECTED

GEM C267

Replace the failed fuses.

Fuse 15 (5A)

Fuse 22 (50A)


Yes GO to F7.

No If fuse 22 (50A) fails, GO to F6 . If fuse 15 (5A) fails, GO to F10 .

F6 CHECK CIRCUIT 1052 (T/BK) FOR SHORT TO GROUND


Measure the resistance between fuse junction panel C243-11, circuit 1052 (T/BK), and ground.






F7 CHECK THE FUSE JUNCTION PANEL


Measure the resistance between fuse junction panel C243 terminal 11 and fuse junction panel C267 terminal 4; and between fuse junction panel C243 terminal 11, and fuse junction panel C267 terminal 16.


Yes GO to F8.


F8 CHECK CIRCUIT 875 (BK/LB) FOR CONTINUITY TO GROUND

GEM C239

Measure the resistance between GEM C239-26, circuit 875 (BK/LB), and ground.


Yes GO to F9.

No REPAIR circuit 875 (BK/LB). CLEAR the DTCs. TEST the system for normal operation.

F9 CHECK CIRCUIT 875 (BK/LB) FOR OPEN



Measure the resistance between GEM C239-14, circuit 875 (BK/LB), and ground.


Yes REFER to Section 418-00.

No REPAIR circuit 875 (BK/LB). CLEAR the DTCs. TEST the system for normal operation.

F10 CHECK THE FUSE JUNCTION PANEL FOR SHORT TO GROUND

Measure the resistance between fuse junction panel C267 terminal 4, and ground.


Yes REFER to Section 418-00.




1998 f-150/250 workshop manual page 1 of 74

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