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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 81 (Engine Controls - Self-Diagnostics - 8.1L) >> Diagnostic Tests >> DTC P0135 & P0155: Ho2S Heater Circuit - Bank 1 & 2, Sensor 1 >> Diagnostic Procedures

Diagnostic Procedures

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  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. NOTE: If DTC P0300 is set, diagnose that DTC first. See DTC P0300: ENGINE MISFIRE DETECTED .

    Allow the engine to cool for one-half hour before proceeding with this diagnostic. This allows the HO2S signal voltage to return to bias voltage, approximately 447 mV.

  2. Install a scan tool. Turn ON the ignition, with the engine OFF. Command the HO2S heater ON with a scan tool. Immediately observe the affected HO2S voltage for 2 minutes. Does the HO2S voltage go from bias voltage to more than or less than 350-550 mV? 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. Are both DTC P0135 and DTC P0155 set? If yes, go to step  6. If no, go to next step.
  5. Turn OFF the ignition. Disconnect the affected HO2S connector. Probe the HO2S heater high control circuit with a test lamp connected to a good ground. Turn ON the ignition, with the engine OFF. Command the HO2S heater ON with a scan tool. Does the test lamp illuminate? If yes, go to step  7. If no, go to step  8.
  6. Disconnect HO2S bank 1 sensor 1 connector. Disconnect HO2S bank 2 sensor 1 connector. Probe the HO2S bank 1 sensor 1 heater high control circuit with a test lamp connected to a good ground. Turn ON the ignition, with the engine OFF. Command the HO2S heater ON with a scan tool. Does the test lamp illuminate? If yes, go to next step. If no, go to step  8.
  7. Connect a test lamp between the affected HO2S heater high control circuit and the HO2S heater low control circuit. Command the HO2S heater ON with a scan tool. Does the test lamp illuminate? If yes, go to step  9. If no, go to step  11.
  8. Disconnect the PCM connector containing the HO2S heater high control circuit. Test the HO2S heater high control circuit for an open or short to ground. Did you find and correct the condition? If yes, go to step  16. If no, go to step  12.
    9. NOTE: Perform the following test on HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1. A condition in either sensor will cause this DTC to set.
  9. Test the HO2S heater high control circuit, sensor side, for a short to the HO2S body. Did you find the condition? If yes, go to step  15. If no, go to next step.
    10. NOTE: Perform the following test on HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1. A condition in either sensor will cause this DTC to set.
  10. Measure the resistance between the HO2S heater high control circuit, sensor side, and the HO2S heater low control circuit, sensor side. Does the resistance of either sensor measure above or below 2-50 ohms? If yes, go to step  15. If no, go to step  13.
  11. Disconnect the PCM connector containing the HO2S heater low control circuit. Test the HO2S heater low control circuit for an open. Did you find and correct the condition? If yes, go to step  16. If no, go to next step.
  12. Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  13. Inspect for poor connections at the harness connector of the affected HO2S. Did you find and correct the condition? If yes, go to step  16. If no, go to step  15.
  14. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to step  16.
  15. Replace the affected HO2S. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
  16. 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.
  17. 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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