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Home >> Chevrolet >> 2001 >> Cavalier LS, 2.2 4 >> Repair and Diagnosis >> External Pages >> Different car >> Section 36 (Engine Controls Self-Diagnostics - 2.4L) >> Diagnostic Tests >> DTC P0140: Ho2S Circuit Insufficient Activity (Bank 1; Sensor 2) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 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. NOTE: Allow engine to cool for one-half hour before proceeding with this diagnostic. This allows the HO2S signal voltage to return to bias voltage, about 447 mV.
  2. Install a scan tool. Turn ignition on, with engine off. Immediately observe the HO2S 2 voltage parameter with a scan tool for 2 minutes. Does the HO2S 2 voltage change from bias voltage to more than or less than the specified range of 300-600 mV? If yes, go to next step. If no, go to step  5 .
  3. Start and allow engine to reach operating temperature. Operate engine at 2000 RPM for 30 seconds. While observing the HO2S 2 voltage parameter with a scan tool, quickly cycle the throttle from closed throttle to wide open throttle, 3 times. Did the HO2S 2 voltage change more than 300 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 off 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 DIAGNOSTIC AIDS  .
  5. Disconnect HO2S 2 connector. Turn ignition on, with engine off. Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S 2 on the engine harness side and a good ground. Connect a 3-amp fused jumper wire between the low signal circuit of the HO2S 2 on the engine harness side and a good ground. Observe the HO2S 2 voltage parameter with a scan tool. Is the HO2S 2 voltage less than 200 mV? If yes, go to step  9 . If no, go to next step.
  6. Remove both jumper wires from the HO2S 2 high signal and low signal circuits. Measure the voltage from the low signal circuit of the HO2S 2 on the engine harness side to a good ground with a Digital Multimeter (DMM). Is the voltage more than 4 V? If yes, go to next step. If yes, go to step  8 .
  7. Test the HO2S 2 high signal circuit for an open. Did you find and correct the condition? If yes, go to step  21 . If no, go to step  16 .
  8. Test the HO2S 2 low signal circuit for an open. Did you find and correct the condition? If yes, go to step  21 . If no, go to step  16 .
  9. Remove both jumper wires from the HO2S 2 high signal and low signal circuits. Inspect the fuse that provides voltage to the HO2S 2 heater. Is the fuse open? If yes, go to step  12 . If no, go to next step.
  10. Turn ignition on, with engine off. Probe the ignition voltage circuit of the HO2S 2 on the engine harness side with a test light that is connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  17 .
  11. Connect a test light between the ignition voltage circuit of the HO2S 2 on the engine harness side and the heater ground circuit of the HO2S 2 on the engine harness side. Does the test light illuminate? If yes, go to step  15 . If no, go to step  18 .
  12. Test the ignition voltage circuit of the HO2S 2 for a short to ground. Replace the fuse that provides voltage to the HO2S 2 Heater. Did you find and correct a short to ground in the ignition voltage circuit? If yes, go to step  21 . If no, go to next step.
  13. Test the HO2S 2 ignition voltage circuit, sensor side, for a short to the HO2S body. Did you find the condition? If yes, go to step  19 . If no, go to next step.
  14. Measure the resistance between the HO2S 2 ignition voltage circuit, sensor side, and the HO2S 2 heater ground circuit, sensor side with a Digital Multimeter (DMM). Does the resistance measure at less than 3 ohms? If yes, go to step  19 . If no, go to DIAGNOSTIC AIDS  .
  15. Inspect for poor connections at the harness connector of the HO2S 2. Did you find and correct the condition? If yes, go to step  21 . If no, go to step  19 .
  16. Inspect for poor connections at the PCM. Did you find and correct the condition? If yes, go to step  21 . If no, go to step  20 .
  17. Repair the open in the HO2S 2 ignition voltage circuit. After repairs, go to step  21 .
  18. Repair the open in the HO2S 2 heater ground circuit. After repairs, go to step  21 .
  19. Replace the HO2S 2. When complete, go to step  21 .
  20. Turn ignition off. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  21. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC  . Does the DTC run and pass? If yes, go to next step. If no, go to step  2 .
  22. Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
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