OBD-II · Engine and powertrain (P)
P0123
Throttle/pedal position sensor A circuit high
What it means
The position sensor A signal voltage is above its valid range. On electronic throttles this is usually the first sensor in the throttle body.
Symptoms
- reduced power or limp mode (EPC light on VW group cars)
- poor or no response to the accelerator
- raised or unstable idle
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | signal wire short to voltage |
| 02 | open sensor ground |
| 03 | failed sensor in the throttle body |
| 04 | corroded or loose connector |
What to check, step by step
- 01Check the battery voltage and charging: low voltage can upset electronic throttle signals
- 02Inspect the throttle body connector and wiring for corrosion, oil or broken pins
- 03Check the 5 V reference, ground and both position signals with a meter or scope
- 04Watch both throttle position signals in live data while the throttle moves: they should change smoothly without dropouts
- 05Replace the throttle body (the sensors are usually built in) and run the throttle adaptation