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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 250 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0140: Ho2S Circuit Insufficient Activity - Sensor 2 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. 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. Turn ignition switch to RUN position, engine OFF. Using the scan tool, command the HO2S 2 heater ON. Wait 15 seconds to allow the HO2S 2 heater current to stabilize. Observe the HO2S 2 heater current parameter using a scan tool. Is the HO2S 2 heater current parameter 0.217-1.56 amps? If yes, go to next step. If no, go to DTC P0141: HO2S HEATER PERFORMANCE - SENSOR 2 .
  3. Start the engine. Operate the engine at normal operating temperature. Operate the engine at 2000 RPM for 30 seconds. Quickly cycle the throttle from closed throttle to wide open throttle 3 times, while observing the HO2S 2 voltage parameter using a scan tool. Did the HO2S 2 change more than 200 mV? If yes, go to next step. If no, go to step  5.
  4. 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 the DTC. See CONDITIONS FOR RUNNING DTC . 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, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.
  5. Turn ignition switch to OFF position. Disconnect the HO2S 2 harness connector. Turn ignition switch to RUN position, engine off. Observe the HO2S 2 voltage parameter using a scan tool. Is the HO2S 2 voltage parameter more than 800 mV? If yes, go to next step. If no, go to step  7.
    6. CAUTION: The sensor may be damaged if the circuit is shorted to a voltage source.
    NOTE: The normal voltage on the high signal circuit is between 400-500 mV.
  6. Check the HO2S 2 high signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  7. Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S 2 harness connector on the engine harness side and the low signal circuit of the HO2S 2 harness connector on the engine harness side. Observe the HO2S 2 voltage parameter using a scan tool. Is the HO2S 2 voltage parameter 400-500 mV? If yes, go to step  9. If no, go to next step.
  8. Remove the jumper wire from the previous step. Check the HO2S 2 heater low control circuit for a short to one of the following circuits:
    • The HO2S 2 low signal circuit.
    • The HO2S 2 high signal circuit.

    Did you find and correct the condition? If yes, go to step  18. If no, go to step  14.

  9. Remove the jumper wire from the previous step. Connect a 3-amp fused jumper wire from the high signal circuit of the HO2S 2 harness connector on the engine harness side and ground. Observe the HO2S 2 voltage parameter using a scan tool. Is the HO2S 2 voltage parameter 400-500 mV? If yes, go to step  11. If no, go to next step.
  10. Remove the jumper wire from the previous step. Check the HO2S 2 low signal circuit for an open. Did you find and correct the condition? If yes, go to step  18. If no, go to step  15.
  11. Measure the voltage from the high signal circuit of the HO2S 2 harness connector on the engine harness side to a good ground using a DMM. Is the voltage more than one volt? If yes, go to next step. If no, go to step  13.
    12. NOTE: The normal voltage on the low signal circuit is 20-100 mV.
  12. Check the HO2S 2 low signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  13. Check the HO2S 2 high signal circuit for open. Did you find and correct the condition? If yes, go to step  18. If no, go to step  15.
  14. Check for an intermittent and for a poor connection at the HO2S 2. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  15. Check for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  16. Replace the HO2S 2. After repair, go to step  18.
  17. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. After replacing PCM, go to next step.
  18. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . 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.
  19. Using a scan tool, observe the 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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