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
1996 Buick Roadmaster LimitedSECTION Diagnostic Procedures
- Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
- Start and warm engine to normal operating temperature. Increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, select ENGINE 1 DATA LIST and monitor Bank 1 HO2S 1 voltage. If voltage is varying outside range of 352-552 mV, go to next step. If voltage is not varying as specified, go to step 4).
- Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data and note parameters. Turn ignition off for about 15 seconds. Start engine and operate vehicle within the conditions required for this diagnostic to run, and as close to conditions recorded in FREEZE FRAME/FAILURE RECORDS as possible. Select DTC function, then enter DTC P0134. If scan tool indicates that this test failed this ignition, go to next step. If scan tool did not indicate that this test failed this ignition, see DIAGNOSTIC AIDS.
- Turn ignition on, with engine off. Disconnect Bank 1 HO2S 1 harness connector. Jumper high and low signal circuits to ground, on PCM harness side. If voltage is less than 200 mV, go to step 8). If voltage is greater than 200 mV, go to next step.
- Remove jumper wire. Using DVOM, check voltage between sensor high and heater ground circuit, on PCM harness side. If voltage is greater than 375 mV, go to next step. If voltage is not as specified, go to step 7).
- Turn ignition off. Disconnect PCM harness connector. Check continuity of Bank 1 HO2S 1 low circuit. Repair as necessary. After repairs, go to step 13). If circuit is okay, go to step 9).
- Turn ignition off. Disconnect PCM harness connector. Check continuity of Bank 1 HO2S 1 signal circuit. Repair as necessary. After repairs, go to step 13). If circuit is okay, go to step 10).
- Check for poor low circuit signal terminal connection at Bank 1 HO2S 1 harness connector. Repair or replace terminal as necessary. After repairs, go to step 13). If terminals are okay, go to step 11).
- Check for poor low signal terminal connection at PCM harness. Repair or replace terminals as necessary. After repairs, go to step 13). If terminals are okay, go to step 12).
- Check for poor signal circuit terminal connection at PCM harness. Repair or replace terminals as necessary. After repairs, go to step 13). If terminals are okay, go to step 12).
- Replace Bank 1 HO2S 1 sensor. After replacing oxygen sensor, go to step 13).
- Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.
- Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0134. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
- Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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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.