The Powertrain Control Module (PCM) monitors the Throttle Position Sensor (TPS) to check for the proper operation of the Throttle Actuator Control (TAC) system. The position of the throttle plate determines the operation of the throttle body. This plate is controlled by the throttle actuator motor.
The P2108 OBD2 diagnostic code P2108 is related to the malfunctioning of the TAC system and is stored due to the TAC system module processor has a wrong performance. When this happens, the TAC system operation is limited by the PCM.