P2105
Throttle Actuator Control System — Forced Engine Shutdown
The TAC monitor commanded an engine shutdown because throttle authority can no longer be guaranteed safely. The most aggressive TAC limp mode — used when both throttle position sensors disagree or the motor is uncontrollable.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
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.
- TPS1 and TPS2 disagree beyond limitCommon
- Throttle motor not controllablePossible
Parts involved
- Throttle Actuator Control
- Throttle Position Sensor
- ECM
P2105 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.