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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Savana and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ON the ignition, with the engine OFF. Does the secondary Air Injection (AIR) pump run constantly? If yes, go to step  25. If no, go to next step.
  3. Install the scan tool. Start and idle the engine for 5 minutes after Closed Loop is achieved. Observe the long term fuel trim parameter on the scan tool. Is the long term fuel trim above 10%? If yes, go to step  14. If no, go to next step.
  4. Turn ON the ignition, with the engine OFF. Command the AIR pump ON and OFF with a scan tool. Does the AIR pump turn ON and OFF? If yes, go to next step. If no, go to step  6.
  5. Install the scan tool. Start the engine and allow it to run for 2 minutes. Verify the engine is running at normal operating temperature and is in Closed Loop. Command the AIR pump ON with the scan tool. Monitor HO2S 1 bank 1 and HO2S 1 bank 2 sensors. Do the HO2S 1 bank 1 and HO2S 1 bank 2 decrease to 100 mV within 6 seconds? If yes, go, see DIAGNOSTIC AIDS . If no, go to step  15.
  6. Turn the ignition to the ON position. Disconnect the AIR pump electrical connector. Probe the AIR pump supply voltage circuit of the AIR pump with a test lamp connected to a good ground. Command the AIR Pump ON and OFF with a scan tool. Does the test lamp turn ON and OFF? If yes, go to step  11. If no, go to next step.
  7. Remove the battery. Remove the air fuse block assembly. Is the AIR fuse open? If yes, go to step  28. If no, go to next step.
  8. Connect the battery cables. Probe the AIR pump relay battery positive voltage circuit, switched side, at the fuse block with a test lamp connected to a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step  40.
  9. Turn the ignition to the ON position. Probe the AIR pump relay ignition 1 voltage circuit, coil side, at the fuse block with a test lamp connected to a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go step  41.
  10. Probe the AIR pump relay control circuit, at the fuse block with a test lamp connected to battery voltage. Command the AIR pump relay ON and OFF. Does the test lamp turn ON and OFF? If yes, go to step  12. If no, go to step  30.
  11. Probe the AIR pump ground circuit of the AIR pump with a test lamp connected to battery voltage. Does the test lamp illuminate? If yes, go to step  37. If no, go to step  45.
  12. Turn OFF the ignition. Remove the AIR pump relay. Connect a 30-amp fused jumper between the battery positive voltage circuit of the AIR relay block and the AIR pump supply voltage circuit at the AIR fuse block. Does the AIR pump turn ON? If yes, go to step  36. If no, go to next step.
  13. Test for an open or a high resistance in the AIR pump battery supply voltage circuit between the AIR relay and the AIR pump with a Digital Multimeter (DMM). Is the resistance 0-5 ohms? If yes, go to step  37. If no, go to step  43.
  14. Run the engine at 1500 RPM for 1 minute. Is the long term fuel trim above 10%? If yes, diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If no, go to next step.
  15. Turn OFF the ignition. Remove the vacuum hose at the shut-off valve. Connect a vacuum pump to the AIR shut-off valve and apply 10 inches of vacuum to the AIR shut off valve. Does the AIR shut-off valve hold vacuum for 30 seconds? If yes, go to next step. If no, go to step  49.
  16. Connect a vacuum gage to the AIR shut-off vacuum hose. Start and idle the engine. Is the vacuum displayed on the gage at 0 in. Hg? If yes, go to next step. If no, go to step  50.
  17. Ensure the vacuum gage is still installed. Command the AIR pump ON and OFF. Does the vacuum displayed on the gage increase to above 10 in. Hg and drop back to zero inches? If yes, go to step  31. If no, go to next step.
  18. Connect the vacuum gage to the AIR solenoid outlet port. Command the AIR pump ON and OFF. Does the vacuum displayed on the gage increase to above 10 in. Hg and drop back to zero inches? If yes, go to step  47. If no, go to next step.
  19. Remove the vacuum hose at the AIR solenoid inlet. Connect a vacuum gage to the vacuum supply hose. Start and idle the engine. Is the vacuum displayed on the gage above 10 in. Hg? If yes, go to step  21. If no, go to next step.
  20. Remove the vacuum check valve from the vacuum supply hose. Connect a vacuum gage to the hose. Start and idle the engine. Is the vacuum displayed on the gage above 10 in. Hg? If yes, go to step  34. If no, clean intake manifold. See INTAKE MANIFOLD CLEANING & INSPECTION under REMOVAL & INSTALLATION in appropriate article in ENGINES.
  21. Probe the AIR solenoid supply voltage circuit of the AIR solenoid with a test lamp connected to a good ground. Command the AIR pump ON and OFF. Does the test lamp turn ON and OFF? If yes, go to next step. If no, go to step  23.
  22. Probe the AIR control solenoid ground circuit of the AIR solenoid with a test lamp connected to battery voltage. Does the test lamp illuminate? If yes, go to step  38. If no, go to step  45.
  23. Is the AIR control solenoid fuse open? If yes, go to step  42. If no, go to next step.
  24. Test the AIR solenoid supply voltage circuit for an open or high resistance and repair as necessary. After repairs, go to step  53.
  25. Remove the AIR pump relay. Turn the ignition to the ON position. Does the secondary Air Injection (AIR) pump run constantly? If yes, go to next step. If no, go to step  27.
  26. Disconnect the AIR pump connector. Probe the air pump supply voltage of the AIR pump with a test lamp connected to a good ground. Does the test lamp illuminate? If yes, go to step  44. If no, see DIAGNOSTIC AIDS .
  27. Probe the AIR pump relay control circuit at the fuse block with a test lamp connected to battery voltage. Does the test lamp illuminate? If yes, go to step  46. If no, go to step  48.
  28. Test the battery positive voltage circuit between the AIR fuse and the AIR pump relay for a short to ground and repair as necessary. Replace the AIR fuse as necessary. Did you find and correct the condition? If yes, go to step  53. If no, go to next step.
  29. Test the AIR pump supply voltage circuit for a short to ground and repair as necessary. Replace the AIR fuse as necessary. Did you find and correct a condition? If yes, go to step  53. If no, go to step  51.
  30. Test the AIR pump relay control circuit for an open or short to voltage. Did you find and correct a condition? If yes, go to step  53. If no, go to step  39.
  31. Remove the right side AIR crossover hose at the right bank exhaust check valve. Turn the ignition to the ON position. Command the AIR pump ON with a scan tool. Does air pressure flow at the crossover hose? If yes, go to step  34. If no, go to next step.
  32. Remove the crossover hose at the AIR shut-off valve. Command the AIR pump ON with a scan tool. Does air pressure flow at the shut-off valve? If yes, go to step  34. If no, go to next step.
  33. Remove the outlet hose at the AIR pump. Command the AIR pump ON with a scan tool. Does air pressure flow at the pump outlet? If yes, go to next step. If no, go to step  35.
  34. Inspect for leaks or restrictions on the following components:
    • AIR shut-off valve
    • Hoses
    • Exhaust Check valves
    • Vacuum Check valve
    • Fittings
    • AIR pipes
    • Exhaust manifolds

    Did you find and correct a condition? If yes, go to step  47. If no, go to next step.

  35. Inspect the AIR inlet and outlet hoses for leaks or restrictions. Did you find and correct a condition? If yes, go to step  53. If no, go to step  51.
  36. Inspect for poor connections at the AIR pump relay block. Did you find and correct a condition? If yes, go to step  53. If no, go to step  48.
  37. Inspect for poor connections at the AIR pump electrical connector. Did you find and correct a condition? If yes, go to step  53. If no, go to step  51.
  38. Inspect for poor connections at the AIR vacuum control solenoid electrical connector. Did you find and correct a condition? If yes, go to step  53. If no, go to step  50.
  39. Inspect for poor connections at the PCM. Did you find and correct a condition? If yes, go to step  53. If no, go to step  52.
  40. Repair the open or short to ground in the battery positive voltage circuit to the AIR pump relay. After repairs, go to step  53.
  41. Repair the open or short to ground in the ignition 1 voltage circuit to the AIR pump relay. Replace fuse E, as necessary. Did you find and correct a condition? If yes, go to step  53. If no, go to step  48.
  42. Repair the short to ground in the AIR solenoid supply voltage circuit and replace the AIR solenoid fuse as necessary. After repairs, go to step  53.
  43. Repair the open or the high resistance or short to ground in the AIR pump supply voltage circuit. After repairs, go to step  53.
  44. Repair the short to voltage in the AIR pump supply voltage circuit. After repairs, go to step  53.
  45. Repair the open or high resistance in the AIR ground circuit. After repairs, go to step  53.
  46. Repair the short to ground in the AIR pump relay control circuit. Did you complete the repair? If yes, go to step  53. If no, go to step  52.
  47. Replace the hoses or components, as necessary. After repairs, go to step  53.
  48. Replace the AIR pump relay. After repairs, go to step  53.
  49. Replace the AIR shut off valve. After repairs, go to step  53.
  50. Replace the AIR vacuum control solenoid. After repairs, go to step  53.
  51. Replace the AIR pump. After repairs, go to step  53.
  52. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  53. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC as specified in the supporting text. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  54. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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