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Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Is DTC P1635 also set? If yes, go to DTC P1635: 5-VOLT REFERENCE LOW . If no, go to next step.
  3. Start the engine. Observe the EGR Position Sensor parameter using a scan tool. Is the EGR Position Sensor parameter less than one percent? If yes, go to next step. If no, go to step  6.
  4. Turn ignition switch to RUN position, engine OFF. Command the EGR valve from zero percent to 100 percent using a scan tool. Is the EGR Position Variance parameter less than 15 percent? If yes, go to next step. If no, go to step  7.
  5. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition switch to OFF position for 30 seconds. Operate the vehicle within the DTC. See CONDITIONS FOR RUNNING . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records Did the DTC fail this ignition? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  6. Turn ignition switch to OFF position. Disconnect the EGR valve position sensor harness connector. Turn ignition switch to RUN position, engine OFF. Observe the EGR position sensor parameter using a scan tool. Is the EGR position sensor parameter less than 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 the EGR valve position signal circuit. Is the 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. Check 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. Check 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. Check 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. Check the EGR valve 5-volt reference circuit 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  15.
  14. Check for an intermittent and for a poor connection at the EGR valve. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  15. Check all 5-volt reference circuits for a short to voltage. If yes, go to step  19. If no, go to next step.
  16. Check for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  19. If no, go to step  18.
  17. Replace the EGR valve. After repair, go to step  19.
  18. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  19. Using a scan tool, clear the DTCs. Turn ignition switch to OFF position. Start the engine. Operate the vehicle within the DTC. See CONDITIONS FOR RUNNING . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  20. Using the scan tool, observe the stored information in CAPTURE INFO. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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