P0120 — Throttle/Pedal Position Sensor/Switch "A" Circuit

What it means

The engine control module has detected a general electrical fault in the signal circuit of throttle or accelerator pedal position sensor A. This sensor is a potentiometer that reports throttle plate or pedal angle, which the ECM uses to calculate engine load, fuel delivery, ignition timing and, on drive-by-wire systems, the commanded throttle opening. Typical symptoms are a lit malfunction indicator lamp, limp-home mode with sharply reduced power, unstable idle and hesitation when accelerating.

Likely causes (most common first)

1. Worn or contaminated resistive track inside the throttle or pedal position sensor
2. Chafed, broken or corroded wiring in the sensor harness
3. Corrosion, water ingress or loose terminals in the sensor connector
4. Loss of the 5 V reference voltage or of the sensor ground from the ECM
5. Sensor incorrectly fitted or misadjusted after throttle body service
6. Faulty engine control module

Can you drive with it?

Short trips are possible in limp-home mode, but power is limited and the fault should be repaired without delay.