The Throttle Actuator Control (TAC) system is controlled by the Powertrain Control Module (PCM) so that the throttle valve opening angle can be appropriate for the driving conditions. To achieve this, the Throttle Position Sensor (TPS) is used. It is mounted on the throttle body, and detects the throttle valve opening angle, and sends this information to the PCM. Then, the PCM commands the throttle motor.
The DTC P2119 OBDII code is set because the PCM has found a malfunction in the CAT system. For this reason, the Check Engine light turns on.