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HOMESERVICE MANUALSOLDSMOBILE2004BRAVADA RWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 52 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS - 4.2L)DIAGNOSTIC TESTSDTC P0140: HO2S CIRCUIT - INSUFFICIENT ACTIVITY - SENSOR 2DIAGNOSTIC PROCEDURES
2004 Oldsmobile Bravada RWD

Diagnostic Procedures

2004 Oldsmobile Bravada RWDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. 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, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: If any other DTCs are set, except HO2S DTCs, refer to other DTCs first before proceeding. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  .
  2. The engine has reached operating temperature. Operate the engine above 1200 RPM for two minutes. With a scan tool, observe the HO2S voltage parameter. Does scan tool indicate HO2S voltage varying outside 425-475 mV? If yes, go to next step. If no, go to step  4 .
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see appropriate TROUBLE SHOOTING - NO CODES article.
  4. Inspect and test for the following conditions:
    • Exhaust leak.
    • The HO2S is installed correctly.
    • Damaged wiring.

    Did you find and correct the condition? If yes, go to step  13 . If no, go to next step.

  5. Turn OFF the ignition. Disconnect the HO2S. Turn ON the ignition. Measure the voltage on the HO2S high signal circuit (PCM side). Does the voltage measure near 450 mV? If yes, go to next step. If no, go to step  8 .
  6. Jumper the HO2S high signal circuit to the HO2S low signal circuit (PCM side). With a scan tool, observe HO2S voltage parameter. Does the scan tool indicate HO2S voltage at or near 0 mV? If yes, go to step  9 . If no, go to next step.
  7. Test the HO2S low signal circuit for an open, high resistance, or short to voltage. Did you find and correct the condition? If yes, go to step  13 . If no, go to step  11 .
  8. Test the HO2S high signal circuit for an open, high resistance, or short to voltage. Did you find and correct the condition? If yes, go to step  13 . If no, go to step  11 .
  9. Test for poor connections at the HO2S. 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. Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicone contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.
  10. Inspect and test for the following conditions:
    • Fuel contamination.
    • Engine oil or coolant consumption.
    • Use of improper RTV sealant.

    Replace the affected HO2S sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  13 .

  11. Test for poor connections at the PCM. Did you find and correct the condition? If yes, go to step  13 . If no, go to next step.
  12. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  13. Clear the DTCs with a scan tool. 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 .
  14. Observe the stored information, Capture Info with a scan tool. 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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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.