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.
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 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage fluctuate rapidly greater than and less than the specified value of 350-550 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, go to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Measure the voltage from the high signal circuit of the HO2S 1 harness connector, on the engine side, to a good ground with a Digital Multimeter (DMM). Is the HO2S voltage within 0.425-0.500 volt? If yes, go to next step. If no, go to step 6.
- Turn ignition off. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit, and the HO2S 1 low reference circuit. Turn ignition on, with engine off. Observe the HO2S 1 voltage on the scan tool. Does the scan tool display less than 25 mV? If yes, go to step 8. If no, go to next step.
- Turn ignition off. Disconnect both PCM connectors. Measure the resistance of each of the following circuits with a DMM: HO2S 1 high signal circuit between HO2S connector and PCM connector, HO2S 1 low reference circuit between HO2S connector and PCM connector low reference loop between PCM harness connector terminals C1-29 and C2-80. Is resistance of each circuit less than 5 ohms? If yes, go to step 11. If no, go to next step.
- Repair the circuit that measured a high resistance or an open. After repairs, go to step 14.
- Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S heater ignition voltage circuit, and HO2S heater low control circuit terminals on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to DTC P0135: HO2S HEATER PERFORMANCE .
- 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 14. If no, go to next step.
- Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 14. If no, go to step 12.
- Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 14. If no, go to step 13.
- Replace the HO2S 1. After repairs, go to step 14.
- 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.
- Using scan tool, observe stored information and 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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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.