P0120 Code: Throttle Position Sensor A Circuit — Causes & Fix
P0120 means a malfunction in the throttle/pedal position sensor "A" circuit — the primary sensor telling the ECM the throttle opening.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $30 – $400
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include a worn TPS/throttle body, a connector fault, or damaged wiring. P0120 is a generic OBD-II powertrain code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer petrol car or light truck regardless of make. Fix the underlying fault, then clear the code with an OBD-II scan tool — it will return if the problem isn't resolved.
Symptoms
- Check engine light on
- Erratic idle, hesitation, or surging
- Reduced power / limp mode
How to fix it
- 1
Inspect the connector and wiring
1. Reseat the throttle body/pedal connector. 2. Check the harness for damage.
- 2
Test/replace the throttle body
1. Watch the TPS sweep on a scan tool. 2. Replace the throttle body if the signal is erratic, then clear the code.
Frequently asked questions
Why is my car in limp mode with P0120?
Electronic throttles limit power when the position signal is unreliable. Fixing the TPS circuit restores normal response.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.