Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSOLDSMOBILE2004BRAVADA RWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 109 (ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 3.4L)DIAGNOSTIC TESTSDTC P0140: HO2S CIRCUIT INSUFFICIENT ACTIVITY (BANK 1; SENSOR 2)DIAGNOSTIC PROCEDURES
2004 Oldsmobile Bravada RWD
Diagnostic Procedures
2004 Oldsmobile Bravada RWDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, 2002 Chevrolet Monte Carlo, and 2002 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
- 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.
- 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 greater than and less than 375-475 mV? If yes, go to next step. If no, go to step 4.
- Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the 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.
- Disconnect the HO2S 2 connector. Turn ignition on, with engine off. Connect a 3-amp fused jumper wire between the HO2S 2 low signal circuit and a good ground. Connect a 3-amp fused jumper wire between the HO2S 2 high signal circuit and a good ground. Observe the HO2S 2 voltage parameter with a scan tool. Does the HO2S 2 voltage measure less than 25 mV? If yes, go to step 7. If no, go to next step.
- With the ignition OFF disconnect the PCM. Leave the HO2S 2 disconnected. Measure the resistance of the HO2S 2 high signal circuit. Measure the resistance of the HO2S 2 low signal circuit. Is the resistance within 0-5 ohms? If yes, go to step 9. If no, go to next step.
- Repair the signal circuit that has an open or high resistance condition. After repairs, go to step 12.
- 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.
- 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.
- 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.
- Replace the HO2S 2. After repairs, go to step 12.
- Turn ignition off. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After replacing PCM, go to next step.
- 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.
- With a scan tool, observe the stored information, 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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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.