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Home >> Pontiac >> 2002 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0135: Ho2S Heater Circuit - Sensor 1 >> Diagnostic Procedures
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Diagnostic Procedures

  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. Allow the engine to idle at operating temperature. Monitor the HO2S 1 Heater Current parameter on a scan tool. Allow the current to stabilize. Is the HO2S 1 Heater Current 0.25-0.85 amp.? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
    4. NOTE: Use a known-good ground. Do not use the HO2S 1 heater low control circuit or the HO2S 1 low reference circuit.
  4. Disconnect the HO2S 1 electrical connector. Turn ON the ignition, with the engine OFF. Probe the HO2S heater ignition voltage circuit at the HO2S 1 electrical connector, on the PCM harness side, with a test lamp connected to ground. Does the test lamp illuminate? If yes, go to step  6. If no, go to next step.
  5. Test the HO2S 1 heater ignition voltage fuse. Is the fuse open? If yes, go to step  11. If no, go to step  12.
  6. Turn OFF the ignition. Connect a test lamp between the HO2S 1 ignition 1 voltage circuit and the HO2S 1 heater low control circuit. Start the engine. Does the test lamp illuminate? If yes, go to next step. If no, go to step  8.
  7. Leave the test lamp connected between the HO2S 1 heater ignition voltage circuit and the HO2S 1 heater low control circuit. Turn OFF the ignition. Turn ON the ignition, with the engine OFF. Does the test lamp illuminate? If yes, go to step  9. If no, go to step  13.
  8. Turn OFF the ignition. Disconnect the PCM connector containing the HO2S 1 heater low control circuit. Measure the resistance of the HO2S heater low control circuit between the PCM harness connector, and the HO2S harness connector using a Digital Multimeter (DMM). Is the resistance 0-5 ohms? If yes, go to step  15. If no, go to step  10.
  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  15.
  10. Test the HO2S 1 heater low control circuit for an open or high resistance condition. Repair as necessary. After repairs, go to step  18.
  11. 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 step  13.
  12. Test the HO2S 1 heater ignition voltage circuit for an open or high resistance condition. Repair as necessary. After repairs, go to step  18.
  13. At the disconnected HO2S 1 pigtail connector, test the HO2S heater ignition voltage circuit for continuity between the following circuits of the HO2S:
    • The HO2S 1 high signal.
    • The HO2S 1 low signal.
    • The HO2S 1 outer shell or a good ground.

    Do any of the circuits measure other than infinite resistance? If yes, go to step  16. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.

  14. Check for poor connections at the harness connector of the HO2S 1. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  15. Check for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  16. Replace the HO2S 1. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  18.
  17. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  18. 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. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  19. 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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