Symptoms of a Failing Throttle Position Sensor (TPS) on a 2000 Cadillac DeVille

The Throttle Position Sensor tells the engine computer (ECM) how far you're pressing the gas pedal. When it fails, the ECM gets wrong data—causing drivability nightmares.

8 Warning Signs

1. Check Engine Light: Codes P0120–P0124, P0220–P0229 (TPS circuit faults).
2. Stalling: At idle, when stopping, or after starting—ECM can't maintain idle air/fuel.
3. Hesitation/Jerking: On acceleration; "dead spots" in pedal travel.
4. Rough/Unstable Idle: RPM fluctuates, engine shakes.
5. Poor Fuel Economy: ECM over-fuels due to false wide-open-throttle signal.
6. Reduced Power/Sluggish Acceleration: ECM limits torque for safety.
7. Throttle Insensitivity: Pedal feels "dead" or delayed.
8. Hard Starting/Long Crank: Wrong air/fuel mix for startup.

Diagnosis & Fix

• Scan for codes (OBD-II).
• Test TPS voltage sweep (0.5V closed → 4.5V WOT) with multimeter.
• Check wiring/connector for corrosion, chafing.
• Replace TPS (mounted on throttle body) – ~$50–$120 part; 30–60 min labor.
• Clear codes, relearn idle (may need scan tool).

Note

These symptoms overlap with MAF sensor, IAC valve, vacuum leaks, fuel pump issues. Proper diagnosis saves money.