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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 258 (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 GMC Sonoma and 2003 Chevrolet S10 Pickup. 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, go to next step.
    2. NOTE: If any other DTCs are set, diagnose affected DTCs before proceeding with this test.
  2. Ensure engine is at operating temperature. Operate engine at greater than 1200 RPM for 2 minutes. Using scan tool, observe HO2S 2 voltage. Does the HO2S voltage read outside the specified range of 400-500 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 off for 30 seconds. Start engine. Operate 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, problem is intermittent.
  4. Inspect and test for exhaust leak, properly installed HO2S 2, or damaged wiring. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  13 . If no, go to next step.
  5. Turn ignition off. Disconnect HO2S harness connector. Turn ignition on, with engine off. With a DVOM, measure voltage on PCM side of the HO2S high signal circuit to ground. Does the HO2S 2 signal voltage measure about 450 mV? If yes, go to next step. If no, go to step  8 .
  6. Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S 2 harness connector 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 harness connector on the engine harness side and a good ground. Observe the HO2S voltage with a scan tool. Does the HO2S signal voltage measure about zero mV? If yes, go to step  9 . If no, go to next step.
  7. Test the low signal circuit for an open circuit or high resistance. Did you find and correct the condition? If yes, go to step  13 . If no, go to step  11 .
  8. Test the high signal circuit for an open circuit or high resistance. Did you find and correct the condition? If yes, go to step  13 . If no, go to step  11 .
  9. Inspect for poor connections at the HO2S. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  13 . If no, go to next step.
    10. NOTE: Determine the cause of contamination before replacing the sensor.
  10. Inspect and test for fuel contamination or improper RTV sealant. Replace HO2S 2. After replacing sensor, go to step  13 .
  11. Inspect for poor connections at the PCM. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  13 . If no, go to next step.
  12. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  13. 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  . 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.
  14. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
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