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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 85 (Engine Controls - Self-Diagnostics - 8.1L) >> Diagnostic Tests >> DTC P1133 & P1153: Ho2S Circuit - Insufficient Switching - 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. Run the engine until the engine reaches normal operating temperature. Monitor the HO2S voltage for the sensor that applies to this DTC with a scan tool. Does the scan tool indicate the HO2S voltage varying above and below 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. Did the DTC fail this ignition? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Turn OFF the ignition. Disconnect the HO2S connector for the sensor that applies to this DTC. Connect a 3-amp fused jumper wire between the HO2S high signal circuit on the engine harness side and a known-good ground. Turn ON the ignition, with the engine OFF. Monitor the HO2S voltage for the sensor that applies to this DTC with a scan tool. Does the HO2S voltage measure below 20 mV? If yes, go to next step. If no, go to step  8.
  5. Remove the fused jumper from the known-good ground. Jumper the HO2S high signal circuit to the HO2S low signal circuit. Monitor the HO2S voltage for the sensor that applies to this DTC with a scan tool. Does the scan tool indicate that the HO2S voltage is less than 20 mV? If yes, go to next step. If no, go to step  9.
  6. Remove the HO2S low signal circuit jumper. Connect a test lamp between the heater high control circuit terminal of the HO2S on the engine harness side and a know good ground. Do not use the HO2S heater ground. Turn ON the ignition, with the engine OFF. Command the HO2S heater ON using the scan tool. Does the test lamp illuminate? If yes, go to next step. If no, go to step  10.
  7. Connect a test lamp between the heater high control circuit terminal, both on engine harness side. 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  12. If no, go to step  11.
  8. Test the HO2S high signal circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  17. If no, go to step  14.
  9. Test the HO2S low signal circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  17. If no, go to step  14.
  10. Test the affected HO2S heater high control circuit for an open, high resistance, or short to ground. Did you find and correct the condition? If yes, go to step  17. If no, go to step  14.
  11. Test the affected HO2S heater low control circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  17. If no, go to step  14.
    12. NOTE: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a White powdery coating. Silicone contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.
  12. Inspect for the following conditions:
    • The use of incorrect silicone RTV sealant.
    • An engine coolant leak into the combustion chamber.
    • Excessive engine oil consumption.
    • Fuel contamination.
    • An exhaust system leak between the engine and the HO2S.

    Did you find and correct the condition? If yes, go to step  17. If no, go to next step.

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