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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. 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. Is DTC P1635 also set? If yes, go to DTC P1635: 5-VOLT REFERENCE 1 CIRCUIT . If no, go to next step.
  3. Start engine. Observe the EGR Position Sensor parameter with a scan tool. Is the EGR Position Sensor parameter less than 1 percent? If yes, go to next step. If no, go to step  6.
  4. Turn ignition on, with engine off. With a scan tool, command the EGR valve from zero percent to 100 percent. Does the desired EGR position remain within 15 percent of the EGR position sensor at all commanded positions? If yes, go to next step. If no, go to step  7.
  5. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Operate vehicle within the Conditions for Running DTC or within the parameters observed in the Freeze Frame/Failure Records. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  6. Turn ignition off. Disconnect EGR valve. Turn ignition on, with engine off. With a scan tool, observe the EGR position sensor parameter. Does the scan tool indicate that the EGR position sensor is at one percent? If yes, go to next step. If no, go to step  10.
  7. Connect a test light between the 5-volt reference circuit of the EGR valve and the low reference circuit of the EGR valve. Does the test light illuminate? If yes, go to next step. If no, go to step  9.
  8. Connect a 3-amp fused jumper wire from the 5-volt reference circuit of the EGR valve to EGR valve position signal circuit. Is EGR position sensor parameter on the scan tool more than 99 percent? If yes, go to step  14. If no, go to step  12.
  9. Connect a test light between the 5-volt reference circuit of the EGR valve and a good ground. Does the test light illuminate? If yes, go to step  11. If no, go to step  13.
  10. Test the EGR valve position signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  11. Test the low reference circuit of the EGR valve for an open or for high resistance. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  12. Test the EGR valve position signal circuit for high resistance or for a high resistance short to ground. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  13. Test the 5-volt reference circuit of the EGR position sensor for an open, a short to ground, or a short to voltage. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  14. Inspect for poor connections at the harness connector of the EGR valve. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  15. Test all 5-volt reference circuits for a short to voltage. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  16. Inspect for poor connections at the PCM harness connector. Did you find and correct the condition? If yes, go to step  19. If no, go to step  18.
  17. Replace EGR valve. See REMOVAL & INSTALLATION - AZTEC & RENDEZVOUS article. After repairs, go to step  19.
  18. Replace PCM. See REMOVAL & INSTALLATION - AZTEC & RENDEZVOUS article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  19. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  20. 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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