P0120
High SeverityThrottle Position Sensor A Circuit
Fuel System
What Does P0120 Mean?
General fault in the TPS circuit. The TPS tells the ECM how far the throttle is open.
Common Fix
Replace TPS or throttle body
Estimated Cost (DIY)
$20 - $150
Symptoms
- ⚠️Erratic idle
- ⚠️Hesitation on acceleration
- ⚠️Surging
- ⚠️Reduced power mode
Common Causes
Faulty TPSlikely
Corroded TPS connectorpossible
Wiring issuepossible
Worn throttle bodypossible
How to Diagnose P0120
- 1Check TPS connector for corrosion
- 2Sweep TPS with scan tool — look for dropouts
- 3Measure TPS voltage at closed and WOT
- 4Replace TPS if erratic
Need to read or clear this code?
Shop OBD2 Scanners on Amazon →Frequently Asked Questions
- Can a dirty throttle body cause P0120?
- Yes — carbon buildup can prevent the throttle from closing fully, confusing the TPS. Clean the throttle body first.
- What is limp mode?
- When the ECM cannot trust the TPS, it limits power to protect the engine. This is called limp mode or reduced power mode.