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
1999 Buick Regal LSSECTION Diagnostic Procedures
- Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
- Turn ignition on. Using scan tool, check if DTC P0300 is also present. If DTC P0300 is present, diagnose DTC P0300 first. If DTC P0300 is not present, go to next step.
- If DTC P0121 or P0122 is present, diagnose affected DTC first. If DTCs are not present, go to next step.
- Using scan tool, select FAILURE RECORDS. Note TP sensor display. If snapshot TP sensor reading is less than zero degrees, go to next step. If snapshot TP sensor reading is not less than zero degrees, go to step 8.
- An intermittent low voltage reading occurred on the TP sensor circuit. Check for possible open or short to ground in TP sensor signal circuit or open in 5-volt reference circuit. Repair as necessary. If circuits are okay, go to next step.
- Slowly depress accelerator from closed throttle to wide open throttle. Note TP sensor reading. Watch for a sudden skip or jump in TP sensor reading. If reading skips or jumps, go to next step. If reading does not skip or jump, fault is not present at this time.
- Check for binding or sticky throttle. Check for chaffed TP sensor wires. Repair as necessary. If no problem is found, go to step 11.
- If snapshot TP sensor reading is greater than 85 degrees, go to next step. If the snapshot of TP sensor reading is not greater than 85 degrees, go to step 6.
- An intermittent high voltage reading occurred on the TP sensor circuit. Check for open in TP sensor ground circuit or short in TP sensor signal circuit. Repair as necessary. If circuits are okay, go to next step.
- Slowly depress accelerator from closed throttle to wide open throttle. Note TP sensor reading. Watch for a sudden skip or jump in TP sensor reading. If reading skips or jumps, go to next step. If reading does not skip or jump, fault is not present.
- Replace TP sensor.
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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.