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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 379 (Engine Controls Self-Diagnostics - 3.4L) >> Diagnostic Tests >> DTC P1133: Ho2S Insufficient Switching - Sensor 1 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. 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. Using a scan tool, clear the DTC and record the Freeze/Frame Failure Records. Observe the HO2S 1 voltage parameter. 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 for this DTC. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running. See CONDITIONS FOR RUNNING . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to next step. If no, problem is intermittent. Go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.
  4. Turn ignition switch to OFF position. Disconnect HO2S 1 harness connector. Turn ignition switch to RUN position, engine off. Measure the voltage between the HO2S 1 high signal circuit on the PCM side to a good ground. Does the voltage measure 425-500 mV? 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 high signal circuit and HO2S 1 low signal circuit. Turn ignition switch to RUN position, engine off. Using a scan tool, monitor the HO2S 1 voltage for the sensor that applies to this DTC. Does scan tool indicate that HO2S 1 voltage is less than 25 mV? If yes, go to step  7. If no, go to next step.
  6. Turn ignition switch to OFF position. Disconnect both PCM 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.
    • Low reference loop between pin C1-29 and pin C2-80 of the PCM connectors.

    Is the resistance of each circuit less than 5 ohms? If yes, go to step  10. If no, go to step  11.

  7. Remove the jumper wire from the previous step. Connect a test light between the HO2S heater ignition voltage circuit and the HO2S heater low control circuit on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to step  4 of DTC P0135: HO2S 1 HEATER PERFORMANCE.
  8. Inspect 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 in order 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. The exhaust system for restrictions. See EXHAUST SYSTEM in SYSTEM & COMPONENT TESTING - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.
    • Evaporative Emissions (EVAP) system malfunction. Inspect the EVAP control system.
    • The fuel pressure. Go to FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.

    Did you find and correct the condition? If yes, go to step  14. If no, go to next step.

  9. Check 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.
  10. Check for an intermittent and for a poor connection at the PCM harness connectors. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  11. Repair the circuit that measured a high resistance or an open. Did you find and correct the condition? After repair, go to step  14.
    12. NOTE: Before replacing the HO2S 1, check and remove any source of contamination.
  12. Replace the HO2S 1 sensor. After repair, go to step  14.
  13. Replace PCM. See POWERTRAIN CONTROL MODULE 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 DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate vehicle within Conditions For Running. See CONDITIONS FOR RUNNING . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  15. Using the scan tool, observe the stored information in CAPTURE INFO. Does 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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