P0122
Throttle/Pedal Position Sensor "A" Low Input
The TPS signal voltage is below the lower acceptable threshold. The ECU usually enters limp-home mode and limits engine torque while the fault is active.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
Common causes
Ordered by how often each turns out to be the cause.
- Signal wire shorted to groundCommon
- TPS internally failedPossible
- 5V reference voltage to TPS missingLess likely
Parts involved
- Throttle Position Sensor
- Throttle Position Sensor Wiring
P0122 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.