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Troubleshooting TechniquesChapter 13 Troubleshooting Techniques © Goodheart-Willcox Co., Inc.
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.
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.
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.
Evaluating Customer InputObtaining 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.
Driver Input Try to talk to person who normally drives vehicleTry 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.
Driveability Worksheet© Goodheart-Willcox Co., Inc.
Assessing Driver InputTry 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.
Assessing Driver InputMost 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.
Assessing Driver InputOwner 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.
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.
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.
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.
Work Order Legal contract with vehicle ownerFill 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.
Work Order After work is finished, list: All work performed Labor timeLabor cost Parts needed and cost of parts Total of any subcontracted work Supply charge Disposal fees © Goodheart-Willcox Co., Inc.
VIN Numbers © Goodheart-Willcox Co., Inc.
Emission-Certification LabelLocated in engine compartment Contains information on: Recommended spark plug gap Ignition timing Routing diagram for hoses © Goodheart-Willcox Co., Inc.
Road Testing Road test may: Reveal or confirm driveability problemsIndicate 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.
Road Testing Some problems can only be found by road testingMost 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.
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.
Road Test Safety ConsiderationsBefore 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.
Road Test Safety ConsiderationsAddress 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.
Road Test Safety ConsiderationsDrive slowly when leaving service area Ensure brakes and steering are working properly Ensure no other problems exist that could cause personal injury or vehicle damage © Goodheart-Willcox Co., Inc.
Road Test Safety ConsiderationsObey all traffic rules Be alert while driving If 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.
Road Testing ProceduresTry to duplicate normal driving conditions Light and heavy acceleration Deceleration Braking Different cruising speeds © Goodheart-Willcox Co., Inc.
Road Testing ProceduresNote 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.
Road Testing ProceduresWhen 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.
Diagnosing Intermittent ProblemsVery 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.
Diagnosing Intermittent ProblemsTry 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.
Performing Visual InspectionsCheck 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.
Performing Visual Inspections(Ford) © Goodheart-Willcox Co., Inc.
Performing Visual InspectionsWhile 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.
Performing Visual InspectionsCheck 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.
Performing Visual InspectionsLook 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.
Principles of DiagnosisBe 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.
Using Service InformationService 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.
Using Service InformationService 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.
Troubleshooting Charts© Goodheart-Willcox Co., Inc.
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.
Diagnosing Electrical ProblemsMinor electrical defects can become major problems Having accurate wiring schematics is crucial First, photocopy schematic for system to be diagnosed © Goodheart-Willcox Co., Inc.
Diagnosing Electrical ProblemsBegin 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.
Diagnosing Charging and Starting SystemsObserve operation as engine runs Charging system Check voltage and amperage output Check for voltage spikes Starting system Observe cranking speed and perform cranking amperage test © Goodheart-Willcox Co., Inc.
Diagnosing Charging and Starting SystemsIf 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.
Diagnosing Engine ProblemsCheck 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.
Diagnosing Engine ProblemsCheck 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.
Diagnosing Engine ProblemsAfter fuel, ignition, and compression systems are tested, check: Emissions system Cooling system Lubrication system Exhaust system © Goodheart-Willcox Co., Inc.
Diagnosing Engine ProblemsMake visual inspection for disconnected hoses or wires If visual inspection does not reveal problem, check operation of entire system © Goodheart-Willcox Co., Inc.
Diagnosing Engine ProblemsYou 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.
Diagnosing Engine ProblemsSometimes, 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.
Diagnosing Computer Control SystemsBefore 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.
Diagnosing Computer Control SystemsECM monitors out-of-range readings from: Sensors Output devices ECM itself Readings are stored as trouble code © Goodheart-Willcox Co., Inc.
Diagnosing Computer Control SystemsIf 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.
Diagnosing Computer Control SystemsProcess 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.
Procedures for Computer System DiagnosticsDriveability 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.
Procedures for Computer System DiagnosticsFind 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.
Procedures for Computer System DiagnosticsCheck all electrical connectors for tightness and cleanliness Check input sensors and related wiring first Most common cause of problems © Goodheart-Willcox Co., Inc.
Procedures for Computer System DiagnosticsNext, 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.
KOEO and KOER Test ProceduresTests 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.
Diagnosing Drive Train ProblemsDrive 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.
Diagnosing Drive Train ProblemsSome 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.
Manual Clutch and Transmission/ Transaxle DiagnosisManual 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.
Automatic Transmissions and TransaxlesAfter 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.
Automatic Transmissions and TransaxlesIf 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.
Diagnosing Other Vehicle SystemsSystems affecting driveability include: Brakes Front and rear suspensions Steering system Air conditioner Cruise control © Goodheart-Willcox Co., Inc.
Diagnosing Other Vehicle SystemsCheck 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.
Diagnosing Other Vehicle SystemsCheck 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.
Diagnosing Other Vehicle SystemsWhen 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.
Diagnosing Problems Caused by Aftermarket EquipmentAdd-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.
Diagnosing Problems Caused by Aftermarket EquipmentExamine system for proper installation Tight 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.
Diagnosing Problems Caused by FuelGasoline-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.
Diagnosing Problems Caused by FuelIf 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.
Deciding on Needed WorkProcess 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.
Deciding on Needed WorkTroubleshooting 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.
Always Perform Additional TestsAdditional 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.
Deciding on Proper Repair StepsAmount 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.
Deciding on Proper Repair StepsSome 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.
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.
Special Tools Used to adjust or disassemble complex assemblyMay be good investment if tools can be reused © Goodheart-Willcox Co., Inc.
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.
Contacting Owner about Needed WorkAfter 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.
Contacting Owner about Needed WorkDefective 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.
Contacting Owner about Needed WorkVehicle 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.
Contacting Owner about Needed WorkBefore 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.
Contacting Owner about Needed WorkIf 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.
Follow-Up after RepairsRecheck 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.
Follow-Up after RepairsAfter work is completed, inspect vehicle for tools Finally, check vehicle for oil, grease, and visible fingerprints © Goodheart-Willcox Co., Inc.
Review What is troubleshooting?The process of diagnosing the cause of a given problem. © Goodheart-Willcox Co., Inc.
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.
Review A. try to duplicate all normal driving conditionsWhen 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.
Review What is an educated guess?A reasonable decision based on testing and the process of elimination. © Goodheart-Willcox Co., Inc.
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.
Review True or False? If the MIL is not on, the ECM does not contain trouble codes. False © Goodheart-Willcox Co., Inc.
Review Manual clutch problems can cause _____, _____, and _____.slipping, vibration, chatter © Goodheart-Willcox Co., Inc.
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. © Goodheart-Willcox Co., Inc.
Glossary Driveability worksheet Educated guessForm that is filled out to simplify the drivability troubleshooting process. Has blanks for driver complaint, test results, repairs needed, and final results. Educated guess Drawing a conclusion based on study of the problem, test readings, and experience. © Goodheart-Willcox Co., Inc.
Glossary Intermittent problems Road testProblems that occur at irregular intervals with no set pattern. Road test Process of driving vehicle upon road for purpose of diagnosing problems and checking efficiency of repairs. © Goodheart-Willcox Co., Inc.
Glossary Root cause of failure SchematicThe basic, sometimes hidden, cause of a failure. Requires additional checking to ensure that the failure does not occur again. Schematic Graphic representation of an electrical, vacuum, or pressure circuit. © Goodheart-Willcox Co., Inc.
Glossary Service information Special toolsSpecifications and instructions for diagnosing and servicing vehicles. May be in printed or electronic form. Much service information is now available on the Internet. Special tools Tool used for a single test or repair purpose. Usually cannot be used for any other purpose. © Goodheart-Willcox Co., Inc.
Glossary Troubleshooting Troubleshooting chartThe process of determining the cause of a problem using logical diagnosis procedures. Troubleshooting chart Chart graphically listing complaints, causes, and possible corrections. A variation of the troubleshooting chart takes the technician through a series of steps to locate and fix a problem. © Goodheart-Willcox Co., Inc.
Glossary Uneducated guess Work orderJumping to the first possible cause that comes to mind, making this a dangerous way of diagnosing problems. Work order Form used to describe vehicle problems and to record diagnosis and repairs. © Goodheart-Willcox Co., Inc.
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