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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 141 (Engine Controls Self-Diagnostics - 5.7L - Bi-Fuel) >> Diagnostic Tests >> DTC P0134 & P0154: Ho2S Bank 1 & 2 Sensor 1 Circuit - Insufficient Activity >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. 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 P1215 also set? If yes, see DTC P1215: GROUND FAULT DETECTION INDICATED  . If no, go to next step.
  3. Use a scan tool in order to establish communication with the AF ECM. Capture the DTC information from the Alternative Fuels ECM into the scan tool. Clear the DTC information using a scan tool. Reset the Fuel Trim values. Start and idle the engine until a normal operating temperature is reached. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC. Is the voltage fixed within 0.10-1.0 V? If yes, go to step  6 . If no, go to next step.
  4. The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
    • Water intrusion of the HO2S connector.
    • An intermittently open HO2S High signal circuit.
    • An intermittently open HO2S Low circuit.
    • An HO2S Low circuit with high resistance to ground.
    • Any Alternative Fuels ECM ground circuits with high resistance to ground.
    • An inoperative HO2S heater.
    • A faulty HO2S or Control Module connector terminal contact.
    • An exhaust system leak, typically within 12 inches up-stream of the HO2S.
    • A defective HO2S.

    Repair any of the above conditions as necessary. Was a condition found and repaired? If yes, go to step  23 . If no, go to next step.

  5. The fault is not present. See DIAGNOSTIC AIDS  . Are any DTCs stored that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  6. Use the scan tool in order to establish communication with the PCM. Start and idle the engine until a normal operating temperature is reached. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC. Is the voltage fixed within 0.10-1.0 V? If yes, go to next step. If no, go to step  18 .
  7. Turn the ignition OFF. Disconnect the HO2S connector for the sensor that applies to this DTC. Jumper the HO2S low circuit to a known-good ground. Jumper the HO2S high signal circuit to a known-good ground. Turn the ignition ON, with the engine OFF. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC. Is the voltage less than 20 mV? If yes, go to step  10 . If no, go to next step.
  8. Turn the ignition OFF. Remove the jumpers from the HO2S terminals. Disconnect the PCM connector containing the HO2S high and low circuits. Use a Digital Multimeter (DMM) in order to measure the continuity of the HO2S high signal circuit and the HO2S low circuit between the control module connector terminal and the HO2S connector terminal, engine harness side. Are both resistances less than 5 ohms? If yes, go to next step. If no, go to step  12 .
  9. Inspect for proper PCM connector terminal contact. Repair the terminals as necessary. Was a terminal repair made? If yes, go to step  23 . If no, go to step  22 .
  10. Remove the jumpers from the HO2S terminals. Connect the Unpowered Test Lamp (J 34142-B) between the HO2S heater ignition feed and heater ground circuit terminals, engine harness side. Turn the ignition ON, with the engine OFF. Does the test lamp illuminate? If yes, go to next step. If no, go to step  13 .
  11. Turn the ignition OFF. Reconnect the HO2S connector. Disconnect the PCM connector containing the HO2S low circuit and the PCM connector containing the control module ground circuits. Use the DMM in order to measure the resistance between the HO2S low circuit terminal and one of the control module ground circuit terminals. Is the resistance less than 500 ohms? If yes, go to step  15 . If no, go to step  14 .
  12. Repair the circuit that measured high resistance. After repairs, go to step  23 .
  13. Repair the HO2S heater ignition or ground circuit. Probable causes include the following conditions:
    • An open circuit.
    • A high circuit resistance.
    • A faulty ground connection.
    • A blown heater fuse (other DTCs may be set).

    After repairs, go to step  23 .

  14. Repair the high resistance between the HO2S low circuit and the control module ground circuit. Probable causes include the following conditions:
    • A faulty HO2S connector terminal contact.
    • An open sensor harness low circuit (requires HO2S replacement).
    • A sensor harness low circuit with high resistance (requires HO2S replacement).
    • A faulty PCM ground connection.
    • A high PCM ground circuit resistance
    • An ungrounded exhaust system.

    After repairs, go to step  23 .

  15. Inspect for exhaust system leaks upstream of the suspect HO2S. The leak may be very small and is typically within 12" (30 cm) of the suspect HO2S. Repair the exhaust as necessary. Was an exhaust system repair made? If yes, go to step  23 . If no, go to next step.
  16. Allow engine to cool to ambient temperature. Use the DMM in order to re-measure the resistance between the HO2S low circuit terminal and a PCM ground circuit terminal. Is the resistance less than 500 ohms? If yes, go to step  20 . If no, go to next step.
  17. Remove the HO2S from the exhaust. Clean the HO2S mounting threads. Apply Anti-Seize Compound (GM P/N 5613695) to the sensor threads. Tighten the HO2S to the proper torque. See OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE. Use the DMM in order to measure the resistance between the HO2S low circuit terminal and a PCM ground circuit terminal. Is the resistance less than 500 ohms? If yes, go to step  23 . If no, go to step  21 .
  18. Inspect the oxygen sensor signal and low circuit for continuity between the AF ECM connector terminals and the oxygen sensor connector terminals. Inspect these circuits for shorts to other circuits or to ground. Ensure that the oxygen sensor, PCM and the AF ECM connectors are disconnected before testing the circuits. Repair the wiring as necessary. Was a wire repair made? If yes, go to step  23 . If no, go to next step.
  19. Replace AF ECM. See ALTERNATE FUEL ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL. Program (flash) AF ECM with correct vehicle software and calibration. See ALTERNATE FUEL ENGINE CONTROL MODULE  under PROGRAMMING. After repairs, go to step  23 .
  20. Perform fuel system diagnosis. See FUEL SYSTEM DIAGNOSIS (BI-FUEL & CNG) under FUEL SYSTEM (BI-FUEL & CNG) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article. Was a CNG fuel system problem found and repaired? If yes, go to step  23 . If no, go to next step.
  21. Replace the HO2S sensor. See OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE. After repairs, go to step  23 .
    22. NOTE: The following control module replacement procedures must all be completed before attempting to operate the vehicle.
  22. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE. Program (flash) PCM with correct vehicle software and calibration. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. To perform CKP variation learn procedure, a switchover to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switchover. Perform CKP system variation learn procedure. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING. After performing repairs and procedures, go to next step.
  23. Reconnect all disconnected or removed components. Use the scan tool in order to clear all DTC information from BOTH the PCM and the AF ECM. Use the scan tool in order to communicate with BOTH the PCM and the AF ECM in order to reset the Fuel Trim values to zero. Start the engine. Operate the vehicle within the Conditions For Running DTC until the scan tool indicates the diagnostic ran. Does the scan tool indicate the diagnostic passed? If yes, system is okay. If no, go to step  2 .
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