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Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. 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. Start the engine. Allow the engine to idle at operating temperature. Observe the HO2S 1 heater current parameter using a scan tool. Allow the HO2S 1 heater current parameter to stabilize. Is the amperage 0.25-0.85 amp? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate vehicle within the Conditions For Running Test. See CONDITIONS FOR RUNNING TEST . 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 INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.1L CENTURY, GRAND PRIX & MALIBU article.
    4. NOTE: Use a known good ground. Do NOT use the Heated Oxygen Sensor (HO2S) 1 heater low control circuit or the HO2S 1 low reference circuit.
  4. Disconnect the HO2S 1 harness connector. Turn ignition switch to RUN position, engine OFF. Probe the HO2S heater ignition 1 voltage circuit, on the engine harness side, using a test light connected to a good ground. Does the test light illuminate? If yes, go to step  6. If no, go to next step.
  5. Test the HO2S 1 heater ignition 1 voltage fuse for an open. Is the fuse open? If yes, go to step  10. If no, go to step  15.
  6. Turn ignition switch to OFF position. Connect a test light between the HO2S ignition 1 voltage circuit and the HO2S heater low control circuit, on the engine harness side connector. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to step  8.
  7. Leave the test light connected between the HO2S 1 heater ignition voltage circuit and the HO2S 1 heater low control circuit. Turn ignition switch to OFF position. Turn ignition switch to RUN position, engine OFF. Does the test light illuminate? If yes, go to step  9. If no, go to step  10.
  8. Turn ignition switch to OFF position. Disconnect the PCM connector containing the HO2S 1 heater low control circuit. Measure the resistance from the HO2S heater low control circuit between the PCM harness connector and the HO2S harness connector using a DMM. Is the resistance 0-5 ohms? If yes, go to step  13. If no, go to step  14.
  9. Test the HO2S 1 heater low control circuit for a short to ground. Did you find and correct the condition? If yes, go to step  18. If no, go to step  13.
  10. Test the HO2S 1 heater ignition voltage circuit for a short to ground and replace the fuse. Did you find and correct the condition? If yes, go to step  18. If no, go to next step.
  11. Measure the resistance from the ignition 1 voltage circuit of the sensor side of the HO2S harness connector to each of the following circuits:
    • The HO2S low reference circuit.
    • Ground.

    Is the resistance less than 5 ohms? If yes, go to step  16. If no, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.1L CENTURY, GRAND PRIX & MALIBU article.

  12. Test for an intermittent and for a poor connection at the HO2S 1 harness connector. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  13. Check for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  14. Repair the open or high resistance in the HO2S heater low control circuit. After repair, go to step  18.
  15. Repair the open or high resistance in the HO2S ignition 1 voltage circuit. After repair, go to step  18.
  16. Replace the HO2S 1. After repair, go to step  18.
  17. 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.
  18. Using scan tool, clear the DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running Test. See CONDITIONS FOR RUNNING TEST . 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 step  2. If no, go to next step.
  19. 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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