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Chapter 13

Chapter 13. Troubleshooting Techniques. Objectives. Explain the basic principles of driveability diagnosis. Evaluate driver input concerning vehicle problems. Make visual checks for underhood problems. Perform a road test.

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Chapter 13

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  1. Chapter 13 Troubleshooting Techniques

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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

  7. Driveability Worksheet

  8. 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

  9. 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

  10. 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

  11. Difficult People • Reasons for anger or hostility vary • Problem 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. VIN Numbers

  17. Emission-Certification Label • Located in engine compartment • Contains information on: • Recommended spark plug gap • Ignition timing • Routing diagram for hoses

  18. Road Testing • Road testmay: • 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

  19. 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

  20. Road Testing • Always try to road test with owner • Ensures 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

  21. 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

  22. 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

  23. Road Test Safety Considerations • Drive 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

  24. Road Test Safety Considerations • Obey 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

  25. Road Testing Procedures • Try to duplicate normal driving conditions • Light and heavy acceleration • Deceleration • Braking • Different cruising speeds

  26. 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

  27. 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

  28. 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

  29. 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

  30. 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

  31. Performing Visual Inspections (Ford)

  32. 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

  33. 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

  34. 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

  35. Principles of Diagnosis • Be sure you correctly interpret all information • Correct root cause of failure • Check simple things first • Make educated guessrather than uneducated guess • Remain calm

  36. Using Service Information • Service informationis source of all: • Vehicle specifications • Diagnostic procedures • Expected test results • Repair procedures • First determine which type of information is needed

  37. 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

  38. Troubleshooting Charts

  39. 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

  40. Diagnosing Electrical Problems • Minor electrical defects can become major problems • Having accurate wiring schematics is crucial • First, photocopy schematic for system to be diagnosed

  41. 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

  42. Diagnosing Charging and Starting Systems • Observe 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

  43. 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

  44. 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

  45. 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

  46. Diagnosing Engine Problems • After fuel, ignition, and compression systems are tested, check: • Emissions system • Cooling system • Lubrication system • Exhaust system

  47. Diagnosing Engine Problems • Make visual inspection for disconnected hoses or wires • If visual inspection does not reveal problem, check operation of entire system

  48. 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

  49. 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

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