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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 84 (Engine Control System Self-Diagnostics - 3.1L Engine) >> 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 Grand Prix, 2002 Chevrolet Malibu, and 2002 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. Allow the engine to idle at operating temperature. Observe the HO2S 2 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 2 voltage is fixed at bias voltage. Vary the engine speed from idle to 3000 RPM several times within 5 seconds. Does the HO2S 2 voltage fluctuate at greater than and less than 375-475 millivolts? 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 off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Disconnect HO2S 2 harness connector. Turn ignition on, with engine off. Connect a 3-amp fused jumper wire between the HO2S 2 harness connector low signal circuit and a good ground. Connect a 3-amp fused jumper wire between the HO2S 2 harness high signal circuit and a good ground. Observe HO2S 2 voltage parameter with scan tool. Does HO2S 2 voltage measure less than 25 millivolts? If yes, go to step  7. If no, go to next step.
  5. Turn ignition off. Disconnect PCM harness connector. Leave HO2S 2 disconnected. Measure resistance of the HO2S 2 high signal circuit and low signal circuit. Is resistance within 0-5 ohms? If yes, go to step  9. If no, go to next step.
  6. Repair signal circuit that has an open or high resistance condition. After repairs, go to step  12.
  7. Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step  12. If no, go to next step.
  8. Inspect for poor connections at the HO2S 2 connector. Did you find and correct the condition? If yes, go to step  12. If no, go to step  10.
  9. Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  10. Replace the HO2S 2. After repairs, go to step  12.
  11. Turn ignition off. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  12. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start 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.
  13. 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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