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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 116 (Engine Controls - Self-Diagnostics - 4.0L) >> Diagnostic Tests >> DTC P0140: Ho2S Bank 1 Sensor 2 Circuit - Insufficient Activity >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Are any DTCs set other than DTC P0140? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. With the engine at the operating temperature, raise and hold the engine speed above 1200 RPM for 2 minutes. Observe the HO2S bank 1 sensor 2 voltage display on the scan tool. Does the scan tool indicate HO2S bank 1 sensor 2 voltage varying outside 300-500 mV? If yes, go to next step. If no, go to step  5.
  4. Turn ON the ignition. Review and record scan tool Failure Records. Operate the vehicle within the Failure Records conditions. Using the scan tool, observe the Specific DTC Information for DTC P0140 until the test runs. Does the scan tool indicate the DTC failed this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  5. Turn OFF the ignition. Raise the vehicle. Disconnect the HO2S bank 1 sensor 2 harness connector. Turn ON the ignition. Jumper the HO2S bank 1 sensor 2 high signal circuit and low signal circuit in the harness connector on the PCM side. Observe the HO2S bank 1 sensor 2 voltage display on the scan tool. Does the scan tool indicate an HO2S bank 1 sensor 2 voltage below 150 mV? If yes, go to step  7. If no, go to next step.
  6. Turn OFF the ignition. Disconnect the PCM connector. Check for the following conditions:
    • An open high signal circuit.
    • An open low signal circuit.
    • Poor terminal connections at the PCM.

    If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  10. If no, go to step  9.

  7. Check for poor terminal connections at the HO2S bank 1 sensor 2 harness connector. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  10. If no, go to next step.
  8. Replace HO2S bank 1 sensor 2. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  10.
  9. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  10. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  11. With a scan tool, observe the stored information, 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.
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