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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. Clear the DTC and record the Freeze/Frame Failure Records. Observe the Heated Oxygen Sensor (HO2S) 1 voltage parameter using a scan tool. Does the HO2S 1 voltage fluctuate rapidly 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 ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running Test or as close to the Freeze Frame/Failure Records data that you observed. See CONDITIONS FOR RUNNING TEST . Does the scan tool indicate that this DTC failed this ignition? If yes, go to next step. If no, refer to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.1L CENTURY, GRAND PRIX & MALIBU article.
  4. Turn ignition switch to OFF position. Disconnect HO2S 1 harness connector. Turn ignition switch to RUN position, engine off. Using a Digital Multimeter (DMM), measure the voltage of the HO2S 1 high signal circuit on the PCM side to a good ground. Does the voltage measure 0.425-0.500 volts? If yes, go to next step. If no, go to step  6.
  5. Turn ignition switch to OFF position. Connect a 3-amp fused jumper wire between the HO2S 1 harness connector high signal circuit and low signal circuit. Turn ignition switch to RUN position, engine off. Use scan tool to monitor HO2S 1 voltage for the sensor that applies to this DTC. Does the scan tool indicate that the HO2S 1 voltage is less than 25 mV? If yes, go to step  8. If no, go to next step.
  6. Turn ignition switch to OFF position. Disconnect both PCM harness connectors. Measure the resistance of each of the following circuits using a DMM:
    • HO2S 1 high signal circuit between HO2S connector and the PCM connector.
    • HO2S 1 low reference circuit between HO2S connector and the PCM connector.
    • HO2S 1 low reference loop between PCM harness connector C1 terminal No. 29 and PCM harness connector C2 terminal No. 80.
    Is the resistance of each circuit less than 5 ohms? If yes, go to step  11. If no, go to next step.
  7. Repair the circuit that measured a high resistance or an open. After repair, go to step  14.
  8. Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S heater ignition voltage circuit and the heater low control circuit terminals on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to DTC P0135: HO2S 1 HEATER PERFORMANCE .
  9. Check for the following that may affect the HO2S operation:
    • HO2S for contamination.
    • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring.
    • The HO2S must have a clean air reference to function properly. This clean air reference is obtained by way of the HO2S wires. Obstruction of the air reference and degraded HO2S performance could result from any attempt to repair the above conditions.
    • Exhaust system leaks or restrictions. See EXHAUST SYSTEM CHECK in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
    • Evaporative Emissions (EVAP) system malfunction. EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
    • The fuel pressure. Incorrect fuel pressure can affect HO2S operation. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.1L CENTURY, GRAND PRIX & MALIBU article.

    Did you find and correct the condition? If yes, go to step  11. If no, go to next step.

  10. Test for an intermittent and for a poor connection at the harness connector of the HO2S 1. Did you find and correct the condition? If yes, go to step  14. If no, go to step  12.
  11. Test for an intermittent and for a poor connection at the PCM harness connector. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
    12. CAUTION: Before replacing the HO2S, check and remove any source of contamination.
  12. Replace HO2S 1. After repair, go to step  14.
  13. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  14. 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. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  15. 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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