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 does not describe the selected car, but rather 7 other vehicles, including the 2002 Pontiac Grand Prix, 2002 Pontiac Bonneville, 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, and 2002 Buick Regal. 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 . 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 using a scan tool. Clear the DTC and record the Freeze Frame/Failure Record if the HO2S 1 voltage is fixed at bias. Does the HO2S 1 voltage fluctuate rapidly above and below 350-550 millivolts? If yes, go to next step. If no, go to step 4.
- Observe the Freeze Frame/Failure Records 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 that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
- Disconnect the HO2S 1 connector. Connect a 3-amp fused jumper wire between the HO2S 1 low signal circuit and a good ground. Turn on the ignition, with the engine off. Observe the HO2S 1 voltage parameter with a scan tool. Does the HO2S voltage read outside 425-475 millivolts? If yes, go to step 7. If no, go to next step.
- Leave the HO2S connector disconnected. Turn on the ignition, with the engine off. Connect a 3-amp fused jumper wire between the HO2S 1 low signal circuit and a good ground. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit and a good ground. Observe the HO2S 1 voltage parameter with a scan tool. Does the HO2S 1 voltage measure less than 25 millivolts? If yes, go to step 9. If no, go to next step.
- With the ignition off, disconnect the PCM. Leave the HO2S disconnected. Measure the resistance of both the HO2S high and HO2S low signal circuits. Do both resistance measurements equal less than 0-5 ohms? If yes, go to step 12. If no, go to step 8.
- Test the affected HO2S signal circuit for short to ground or voltage. Did you find and correct the condition? If yes, go to step 15. If no, go to step 12.
- Repair the signal circuit that measured an open or high resistance. After repairs, go to step 15.
- Remove jumpers from the HO2S 1 signal terminals. Connect a test lamp between the HO2S 1 heater, ignition 1 and ground terminals at the HO2S harness connector. Turn on the ignition, with the engine off. Does the test lamp illuminate? If yes, go to next step. If no, see DTC P0135: HO2S HEATER PERFORMANCE - SENSOR 1 .
- Before continuing inspect for the following conditions that may affect the HO2S operation:
- HO2S contamination. Inspect the HO2S for contamination.
- Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance.
- Do not damage the sensor pigtail and harness wires in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems.
- Ensure the sensor or vehicle lead wires should not be bent sharply or kinked. Sharp bends or kinks could block the reference air path through the lead wire.
- Do not remove or defeat the oxygen sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance.
- Ensure that the peripheral seal remains intact on the vehicle harness connector in order to prevent damage due to water intrusion. The engine harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed.
- Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring.
- The HO2S must have a clean air reference in order to function properly. This clean air reference is obtained by way of the HO2S wires. Obstruction of the air reference and degraded HO2S performance could result from any attempt to repair the above conditions.
- Exhaust system leaks or restrictions.
- Evaporative (EVAP) emissions canister purge Inspect the EVAP control system.
- The fuel pressure. Incorrect fuel pressure can affect HO2S operation.
NOTE: 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.NOTE: Do not remove this pigtail from either the Heated Oxygen Sensor (HO2S) or the Oxygen Sensor (O2S). Removing the pigtail or the connector will affect sensor operation. Handle the oxygen sensor carefully. Do not drop the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Do not use cleaning solvents of any type. Do not repair the wiring, connector or terminals. Replace the oxygen sensor if the pigtail wiring, connector, or terminal is damaged. This external clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance. The following guidelines should be used when servicing the heated oxygen sensor:Did you find and correct the condition? If yes, go to step 15. If no, go to next step.
- Before continuing, inspect for poor connections at the affected HO2S connector. Did you find and correct the condition? If yes, go to step 15. If no, go to step 13.
- Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 15. If no, go to step 14.
- Replace the affected HO2S. After repairs, go to step 15.
- Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After repairs, go to next step.
- Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within Conditions for Running DTC. Does DTC run and pass? If yes, go to next step. If no, go to step 2.
- Using scan tool, observe stored information. Does scan tool displays any DTCs that have not been 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.