Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

1. PublisherThe Goodheart-Willcox Co., Inc.Tinley Park, Illinois PowerPoint for Modern Automotive Technology by Russell Krick

2. Chapter 46 Advanced Diagnostics

3. Contents • Advanced diagnostics • Vacuum and pressure gauge tests • Vacuum pump tests • Diesel engine testers • Advanced scan tools • Checking computer terminal values • Using a breakout box (Continued)

4. Contents • Isolating electromagnetic interference • Using a digital pyrometer • Finding temperature-related performance problems • Using a dynamometer • Using an oscilloscope • Engine analyzer (computer analyzer)

5. Advanced Diagnostics Advanced methods used to troubleshoot difficult-to-locate problems

6. Diagnostic Techniques and Tools • By using some advanced techniques and tools, a technician can diagnose the most difficult problems • Some tools that may be used: • vacuum and pressure gauge • scan tool • breakout box • engine analyzer with oscilloscope

7. Strategy-Based Diagnostics

8. Troubleshooting Chart

9. Vacuum and Pressure Gauge Tests

10. Vacuum Gauge • Measures pressure that is lower than atmospheric pressure • Used for: • fuel pump vacuum tests • vacuum pump testing • intake manifold vacuum testing • vacuum solenoid testing

11. Pressure Gauge • Measures pressure that is higher than atmospheric pressure • Used for: • fuel pump output pressure testing • turbocharger boost testing • exhaust back pressure testing

12. Vacuum Gauge Diagnosis

13. Vacuum-Pressure Gauge Set up to measure boost on a road test

14. Vacuum Pump Tests Used to check vacuum-actuateddevices and vacuum diaphragms

15. Hand Vacuum Pump Connect the pump, pump the handle, and see if the device holds a vacuum

16. Diesel Engine Testers • A set of pressure gauges and valves used to measure injector system pressure • Measure various operating parameters: • fuel pump pressure and volume • injector operation • lubrication system pressure

17. Diesel Engine Testers

18. Advanced Scan Tools In addition to retrieving trouble codes, modern scan tools can be used for advanced diagnostic procedures

19. Advanced Scan Tool Tests • Snapshot • instantaneous reading of the operating parameters present when a problem occurs • useful when intermittent problems occur • program the scan tool for a road test • when the symptom occurs, capture the data • return to the shop and review the snapshot data

20. Advanced Scan Tool Tests • Datastream • “live” electrical values • read the scan tool screen to see computer input and output values

22. Advanced Scan Tool Tests • Actuator tests • most scan tools can switch computer-controlled actuators on and off • allows the technician to verify operation • the scan tool can fire an ignition coil, control the idle speed motor, disable a fuel injector, and perform a balance test

23. Checking Computer Terminal Values

24. Computer Terminal Voltage Checks • Use a digital voltmeter • Probe between the computer terminals and ground • Do not pierce the wires • Compare the terminal voltages to specified values

25. Terminal Voltage Chart

26. Breakout Box • Allows the technician to check electrical values at specific pins on an ECM or in the system the ECM controls • Inserted into wiring harness at the ECM

27. Breakout Box

28. Isolating Electromagnetic Interference

29. Electromagnetic Interference • Occurs when an induced voltage enters another system’s wiring • Sources: • loose, misrouted, or unshielded plug wires • police and CB radios • aftermarket accessories • May cause noise in stereo speakers or a computer-controlled system malfunction

30. Isolating Interference • Turn off or disable circuits or devices • remove the alternator drive belt • turn accessories on and off • If the problem goes away, the cause has been isolated • Use an AM radio tuned between stations to probe for sources

31. Using a Digital Pyrometer

32. Digital Pyrometer • An electronic device used to measure temperature • engine operating temperature • exhaust temperature—catalytic converter • coolant temperature • sensor temperature • ambient temperature • air conditioning system temperatures

33. Finding Temperature-Related Performance Problems

34. Finding Temperature-Related Problems Freeze spray on the ECM

35. Finding Temperature-Related Problems Heat gun on the ECM

36. Using a Dynomometer

37. Dynamometer • Measures power output by loading the engine • Check acceleration, maximum power, and on-road performance characteristics

38. Dynamometer Using a five-gas analyzer witha dynamometer

39. Using a Oscilloscope

40. Oscilloscope • Displays voltages in relation to time • Produces a line on a cathode ray tube or liquid crystal screen

41. Oscilloscope Screen A. 25,000 volt scale B. 50,000 volt scale C. Time scale milliseconds D. Time scale degrees

42. Scope Sweep Rate • Frequency or time division on screen • Affects the horizontal, or time, measurement • Set to match the waveform frequency to be analyzed • a low sweep ratecompresses the signal • a high sweep rateexpands the signal

43. Ignition Patterns • Primary • low voltage ignition components • the secondary circuit cannot work properly unless the primary circuit is in good condition • Secondary • high voltages needed to fire the spark plugs

44. Primary Waveform

45. Secondary Waveform

46. Scope Test Patterns A. Superimposed display Patterns on top of each other—checks that all patterns are uniform B. Parade display Patterns side by side in firing order—compares firing voltages C. Stacked display Cylinders one above the other—compares duration of events

47. Distributorless Waveform • True spark is on compression stroke • Wasted spark is on exhaust stroke

48. Magnetic Sensor Pattern Probe across sensor leads

49. Hall-Effect Sensor Oscilloscope connection

50. Hall-Effect Sensor Pattern The sensor signal frequency should increase as engine speed increases