P2108 indicates the powertrain control module (PCM) has detected a performance problem within the Throttle Actuator Control (TAC) system. The module monitors the electronic throttle body and its actuators, and sets this code when signals are out of expected range, there is a mechanical failure, or the system cannot achieve commanded throttle positions.
The most common cause - the internal electric motor or gear mechanism that opens/closes the throttle plate wears out, binds, or fails electrically, preventing proper throttle position control.
Damaged, corroded, or loose wiring/connectors in the throttle actuator control circuit can cause intermittent or complete signal loss, triggering the code.
The TP sensor provides feedback to the PCM about actual throttle position. If it sends incorrect or erratic signals, the module cannot verify proper performance and sets a fault.
Unmetered air entering the intake manifold (from cracked hoses, bad gaskets, or vacuum leaks) can cause the throttle system to operate outside expected parameters.
Weak battery, failing alternator, or poor ground connections can cause the electronic throttle system to malfunction due to insufficient electrical supply.
A failed or faulty powertrain control module is possible but rare; this should be the last diagnosis after all other causes are ruled out.
Rarely. The throttle body and wiring issues are by far the most common causes. The PCM should only be considered after all other components and circuits have been thoroughly tested and ruled out.
The vehicle will typically enter fail-safe (limp) mode with reduced power to prevent potential safety issues. While you may be able to drive slowly to a repair facility, continued operation risks leaving you stranded or causing further damage.
Yes. Low voltage to the electronic throttle control system can cause intermittent or false fault codes. Always ensure the battery and charging system are functioning properly before replacing throttle components.
Disconnecting the battery may clear the code temporarily, but if the underlying fault (such as a failing throttle motor or wiring issue) remains, the code will return almost immediately upon driving.