OBD-II · Engine and powertrain (P)
P0121
Throttle/pedal position sensor A range/performance
What it means
Throttle or pedal signal correlation is outside the expected range.
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 | dirty electronic throttle |
| 02 | worn pedal sensor |
| 03 | adaptation needed after cleaning |
| 04 | connector fault |
| 05 | sensor reference voltage or ground fault |
What to check, step by step
- 01Check for other throttle, MAF or MAP codes
- 02Inspect the throttle body for carbon or oil build-up and clean it if needed
- 03Run the throttle adaptation (basic settings) with a scan tool after cleaning
- 04Watch sensor A against sensor B in live data through the full throttle travel
- 05Check the connector, reference voltage and ground, then replace the throttle body if the sensor is worn