permission granted to reproduce for educational use only. 2 © goodheart-willcox co., inc. chapter...
TRANSCRIPT
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.2
Chapter 13
Troubleshooting Techniques
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.3
Objectives
Explain the basic principles of driveability diagnosis.
Evaluate driver input concerning vehicle problems.
Make visual checks for underhood problems.
Perform a road test.
Describe the basic methods of diagnosing driveability problems caused by engine systems.
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.4
Objectives
Explain the basic methods of diagnosing driveability problems caused by the vehicle drive train.
Describe the basic methods of diagnosing driveability problems caused by computer control systems.
List factors to be considered when deciding to adjust, rebuild, or replace parts.
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.5
Troubleshooting
Ability to accurately troubleshoot separates successful automotive technicians from “parts swappers”
Ability to apply logical diagnostic process can be improved with study and experience
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.6
Evaluating Customer Input
Obtaining information from driver is first and most important part of diagnosis
Often allows some preliminary testing to be bypassed
Allows technician to focus on most likely source of problem
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.7
Driver Input
Try to talk to person who normally drives vehicle
Try to get accurate description of problem before beginning any work
Driver can usually provide some idea of past service problems and maintenance
Carefully evaluate what driver says
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.8
Driveability Worksheet
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.9
Assessing Driver Input
Try to estimate driver’s attitude and level of automotive knowledge
Driver can unintentionally mislead technician
Pay attention to:Hand gestures
Body language
Simulation of noises heard
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.10
Assessing Driver Input
Most customers are not familiar with automobile operation
Never accept driver’s diagnosis until you verify it
Driver may be overreacting to normal condition
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.11
Assessing Driver Input
Owner may downplay symptoms, hoping for inexpensive repair
Never give uninformed estimates, even if problem seems obvious
Explain to customer diagnostic charge is more cost effective than paying for service that may not fix problem
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.12
Difficult People
Reasons for anger or hostility varyProblem was not solved during previous visit
Customer fears repairs will be too expensive
Customer is upset over inconvenience
Customer is in bad mood unrelated to vehicle problem
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.13
Difficult People
Dealing with customers requires tact and understanding
Talk in calm tones
Avoid getting angry yourself
Keep owner informed about repair process as frequently as possible
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.14
Difficult People
Allow customers to feel they are part of diagnostic and repair process
Once problem is located, inform customer of cause and what is needed to correct problem
If practical, show customer defective part and explain why it is defective
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.15
Work Order
Legal contract with vehicle owner
Fill out completely, even for simple services
Begin work order by listing date and filling out:
Customer information
Vehicle information, including VIN
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.16
Work Order
After work is finished, list:All work performed
Labor time
Labor cost
Parts needed and cost of parts
Total of any subcontracted work
Supply charge
Disposal fees
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.17
VIN Numbers
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.18
Emission-Certification Label
Located in engine compartment
Contains information on:Recommended spark plug gap
Ignition timing
Routing diagram for hoses
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.19
Road Testing
Road test may:Reveal or confirm driveability problems
Indicate specific problem areas and what further tests need to be made
Determine that perceived driveability condition is normal, and no further testing is needed
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.20
Road Testing
Some problems can only be found by road testing
Most problems reveal themselves in less than 15 minutes
When possible, try to duplicate exact conditions under which driver says problem occurs
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.21
Road Testing
Always try to road test with ownerEnsures owner and technician are talking about same problem
Saves valuable time
Avoids diagnosis and repair of problem that does not fix what customer wanted fixed
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.22
Road Test Safety Considerations
Before beginning road test, check to ensure vehicle can be safely driven
Check:Exterior damage
Tire inflation and condition
Turn signals, brake lights, horn
Brake pedal
Steering wheel
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.23
Road Test Safety Considerations
Address any safety-related equipment problems before road testing
Check vehicle fuel level
Wear seat belt at all times
If radio is on, turn it off
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.24
Road Test Safety Considerations
Drive slowly when leaving service areaEnsure brakes and steering are working properly
Ensure no other problems exist that could cause personal injury or vehicle damage
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.25
Road Test Safety Considerations
Obey all traffic rules
Be alert while drivingIf necessary to monitor scan tool readings or look for problem while vehicle is driven, have assistant drive as you monitor the situation
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.26
Road Testing Procedures
Try to duplicate normal driving conditionsLight and heavy acceleration
Deceleration
Braking
Different cruising speeds
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.27
Road Testing Procedures
Note response of engine and related systems
Be alert for:Noises or vibrations
Harshness
Engine miss or hesitation
Transmission shifts
Operation of brake and steering systems
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.28
Road Testing Procedures
When specific problem is identified, look for conditions related to problem
Note if other vehicle parts or driving conditions affect problem
Note all factors related to problem before returning to shop
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.29
Diagnosing Intermittent Problems
Very difficult to diagnose
Usually occur only under certain conditions
Can be related to:Temperature
Humidity
Certain vehicle operations
In response to certain tests by ECM
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.30
Diagnosing Intermittent Problems
Try to recreate exact conditions under which problem occurred
If road testing does not duplicate problem, other types of testing will need to be done
Essential to closely follow principles of strategy-based diagnostics
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.31
Performing Visual Inspections
Check for visible problems before performing diagnostic tests
Use sight, smell, hearing
If problem is not related to cold operation, leave engine running at first
Stop engine before investigating any part near hot or moving parts
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.32
Performing Visual Inspections
(Ford)
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.33
Performing Visual Inspections
While under hood, check level and condition of:
Engine oil
Coolant in recovery tank
Automatic transmission fluid
Note any leaks
Note any disconnected hoses or air intake ducts
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.34
Performing Visual Inspections
Check air and PCV filters for clogging
Make sure PCV valve and hose are not plugged
Check condition of drive belts, especially alternator belt
If engine has serpentine belt, check condition of belt tensioner
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.35
Performing Visual Inspections
Look for prior work on vehicle if no history available
Signs of abuse or tampering
Any engine part that has been removed or replaced by non-stock parts
Aftermarket add-on equipment that can affect vehicle operation
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.36
Principles of Diagnosis
Be sure you correctly interpret all information
Correct root cause of failure
Check simple things first
Make educated guess rather than uneducated guess
Remain calm
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.37
Using Service Information
Service information is source of all:Vehicle specifications
Diagnostic procedures
Expected test results
Repair procedures
First determine which type of information is needed
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.38
Using Service Information
Service information is available as:Manufacturer and general information
Troubleshooting charts
Electrical, vacuum, and information flow schematics
Be sure to use specific information for model and year of vehicle
Protect service information from damage
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.39
Troubleshooting Charts
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.40
Schematics
Traces path from beginning of wire, hose, or information trail to its end
May show how information flows to and from ECM
Make copies of needed pages and trace on copies, not original
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.41
Diagnosing Electrical Problems
Minor electrical defects can become major problems
Having accurate wiring schematics is crucial
First, photocopy schematic for system to be diagnosed
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.42
Diagnosing Electrical Problems
Begin at power source and physically trace wiring back to system ground connection
As each connector, length of wire, and component is tested and checked, mark off component on photocopy
You will eventually isolate the defective wire, connector, or component
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.43
Diagnosing Charging and Starting Systems
Observe operation as engine runs
Charging systemCheck voltage and amperage output
Check for voltage spikes
Starting systemObserve cranking speed and perform cranking amperage test
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.44
Diagnosing Charging and Starting Systems
If starting problem is caused by parasitic draw, begin checks at fuse block
Pull fuses one at a time until circuit causing draw is isolated
Copy schematics for affected circuits and trace each circuit until problem is isolated
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.45
Diagnosing Engine Problems
Check fuel, ignition, and compression systems first
Unless there is good reason to look at another part of vehicle
More than one part of single system may cause same symptom
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.46
Diagnosing Engine Problems
Check all possible causes of problem in basic engine systems before making repairs
Dynamic compression test is common diagnostic method
Cylinders are disabled individually
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.47
Diagnosing Engine Problems
After fuel, ignition, and compression systems are tested, check:
Emissions system
Cooling system
Lubrication system
Exhaust system
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.48
Diagnosing Engine Problems
Make visual inspection for disconnected hoses or wires
If visual inspection does not reveal problem, check operation of entire system
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.49
Diagnosing Engine Problems
You may need to check cooling system for internal leaks or check engine oil pressure by installing pressure gauge
If suspected system is controlled by ECM, check for related trouble codes
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.50
Diagnosing Engine Problems
Sometimes, problem can only be determined by partial disassembly
Before considering major engine disassembly, all other possibilities should be reconsidered and eliminated
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.51
Diagnosing Computer Control Systems
Before beginning diagnosis on vehicles equipped with on-board computers:
Obtain proper service information and other information for computer system
Thoroughly check all non-computer systems
Check ECM memory for trouble codes
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.52
Diagnosing Computer Control Systems
ECM monitors out-of-range readings from:
Sensors
Output devices
ECM itself
Readings are stored as trouble code
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.53
Diagnosing Computer Control Systems
If MIL is on or flashing, ECM contains trouble codes
If MIL is not on, ECM may still contain stored codes
Always perform code retrieval process before proceeding further
Once codes are identified, make further tests as identified in service information
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.54
Diagnosing Computer Control Systems
Process of elimination isolates computer system parts that cannot be tested
ECM
Ignition module
Start by testing all parts that can be tested
If all testable parts check out okay, non-testable part is most likely cause
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.55
Procedures for Computer System Diagnostics
Driveability problems may be caused by defects not related to ECM or ECM-controlled system
Always look for obvious problems first
If no obvious defects are found, retrieve trouble codes from ECM memory
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.56
Procedures for Computer System Diagnostics
Find out what code indicates, and look for defects that could set that code
If basic engine and drive train systems are operating correctly, computer control system may be at fault
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.57
Procedures for Computer System Diagnostics
Check all electrical connectors for tightness and cleanliness
Check input sensors and related wiring first
Most common cause of problems
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.58
Procedures for Computer System Diagnostics
Next, check:Output solenoids and other output devices
Motors
Ignition modules
Injectors
If input devices, output devices, and related wiring are okay, ECM is defective
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.59
KOEO and KOER Test Procedures
Tests performed with ignition on and either engine running or not running
Key-on, engine-off (KOEO) tests
Key-on, engine-running (KOER) tests
Comparing KOEO and KOER readings often helps to pinpoint problem
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.60
Diagnosing Drive Train Problems
Drive train parts can affect driveability by incorrectly transmitting engine power
Defective pressure switches can send improper signals to ECM
Defective solenoids can fail to perform ECM output commands
Other problems include noise, vibration, and harshness from worn parts
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.61
Diagnosing Drive Train Problems
Some defects can be spotted by raising vehicle on lift, such as:
Worn U-joints or CV joints
Oil on clutch facings
Other problems will only show up when vehicle is driven
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.62
Manual Clutch and Transmission/ Transaxle Diagnosis
Manual clutch problems can cause slipping, vibration, and chatter
Check clutch by slowly engaging it with:
Engine running
Vehicle stopped
Transmission in first gear
(Subaru)
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.63
Automatic Transmissions and Transaxles
After checking level and condition of transmission fluid, drive vehicle enough to shift through all speed ranges
Check that shifts are smooth, without slippage, and occur at proper times and speeds
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.64
Automatic Transmissions and Transaxles
If used, try adjusting throttle linkage, then recheck shift pattern
Check that torque converter clutch is applying when it should
If problem cannot be corrected by adjustments, refer to service information for repair procedure
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.65
Diagnosing Other Vehicle Systems
Systems affecting driveability include:Brakes
Front and rear suspensions
Steering system
Air conditioner
Cruise control
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.66
Diagnosing Other Vehicle Systems
Check and inspect each system’s components
Look for obvious problems, including missing or loose drive belts
Look for loose electrical connections on alternator and air conditioning
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.67
Diagnosing Other Vehicle Systems
Check air conditioning for:Proper refrigerant charge
Problems that could make compressor cycle excessively or affect engine operation
Refrigerant leaks at fittings
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.68
Diagnosing Other Vehicle Systems
When possible, drive vehicle to detect problems
Road test may quickly located problems in suspension, brakes, and cruise control system
If symptoms or codes occur in road test, but not in shop, defect may be in system operating when vehicle moves
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.69
Diagnosing Problems Caused by Aftermarket Equipment
Add-on equipment may cause problems due to:
Improper installation
Electromagnetic interference
Poor connections to battery power and chassis ground are most frequent mistakes
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.70
Diagnosing Problems Caused by Aftermarket Equipment
Examine system for proper installationTight connections
Components installed in locations that do not interfere with other systems
Wiring cleanly routed, tied together, and preferably installed in plastic looms
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.71
Diagnosing Problems Caused by Fuel
Gasoline-related driveability problems should be considered if vehicle has problems such as:
Hard starting
Hesitation
Surging
Rough idles before engine reaches normal operating temperature
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.72
Diagnosing Problems Caused by Fuel
If vehicles systems appear okay, suggest owner try another gasoline brand
If owner uses premium in vehicle that does not require it, suggest lower grade
Using wrong grade of diesel fuel in diesel engine may cause driveability problems in cold weather
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.73
Deciding on Needed Work
Process of interpreting results of all diagnostic tests
Before condemning part based on test results, review its interaction with engine and vehicle systems
Decide if part in question can cause particular test reading or symptom
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.74
Deciding on Needed Work
Troubleshooting charts and other diagnostic data can be great asset
Good troubleshooting chart:Lists all possible causes of problem
Allows parts to be checked in logical sequence
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.75
Always Perform Additional Tests
Additional testing is especially important when suspected part is solid-state, or otherwise untestable device
Most are too expensive to randomly replace
Making further checks to confirm problem is always good idea
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.76
Deciding on Proper Repair Steps
Amount and type of needed corrective actions must be determined
Parts that interact with defective part may also need to be changed
For example, replacing rotor when distributor cap is replaced
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.77
Deciding on Proper Repair Steps
Some parts, while theoretically serviceable, are almost always replaced
Factors to consider when deciding to adjust, rebuilt, or replace part:
Ease of adjustment
Need for special tools
Cost of replacement part
Possibility that old part will fail again
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.78
Making Adjustments
If part is easily adjustable, adjust it before rebuilding or replacing
Do not get too involved in trying to adjust stubborn problem
If there is any doubt about whether adjustment has corrected problem, replace part
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.79
Special Tools
Used to adjust or disassemble complex assembly
May be good investment if tools can be reused
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.80
Rebuild or Replace?
Weigh investment in materials and time against cost of new part
Price of new or remanufactured part is often less than charge to rebuild old part
Many repair shops and vehicle manufacturers recommend replacement of complete assemblies
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.81
Contacting Owner about Needed Work
After determining parts and labor necessary to correct problem, contact customer for authorization to perform repairs
Never assume customer will want work done
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.82
Contacting Owner about Needed Work
Defective part or problem may be covered by warranty or guarantee
Vehicle must be returned to approved service facility for repairs
If vehicle is leased, leaseholder is actual owner and may have to approve repairs
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.83
Contacting Owner about Needed Work
Vehicle may be covered by extended warranty or service contract
Forms of insurance
Necessary to file claims for expenses
In some cases, approval must be granted from insurer before repair work can begin
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.84
Contacting Owner about Needed Work
Before talking to anyone about vehicle, be prepared to supply this information:
Exactly what needs to be done and why
Careful breakdown of both part and labor costs
Approximate time when vehicle will be ready
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.85
Contacting Owner about Needed Work
If it is suspected that problem will require further disassembly, make sure customer understands:
Further diagnosis may be needed
Costs may increase
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.86
Follow-Up after Repairs
Recheck vehicle to ensure problem has been corrected
Check that vehicle operates properly and meets emission standards
Always recheck vehicle, even if defect is minor
Problem may have been easily fixed, but caused by another vehicle defect
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.87
Follow-Up after Repairs
After work is completed, inspect vehicle for tools
Finally, check vehicle for oil, grease, and visible fingerprints
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.88
Review
What is troubleshooting?
The process of diagnosing the cause of a given problem.
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.89
Review
What is a work order?
A legal contract between the repair facility and the customer that describes the work to be done.
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.90
Review
When road testing a vehicle, _____.
A. try to duplicate all normal driving conditions
B. drive quickly from the service area to test acceleration
C. ask the customer to wait at the shop
D. None of the above.
A. try to duplicate all normal driving conditions
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.91
Review
What is an educated guess?
A reasonable decision based on testing and the process of elimination.
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.92
Review
Which three systems should be checked first when diagnosing an engine problem?
The fuel, ignition, and compression systems should be checked first.
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.93
Review
True or False? If the MIL is not on, the ECM does not contain trouble codes.
False
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.94
Review
Manual clutch problems can cause _____, _____, and _____.
slipping, vibration, chatter
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.95
Review
What must be considered when deciding whether to rebuild or replace a part?
The investment in materials and time must be weighed against the cost of a new part.