DTC P0505: Description

The DTC P0505 Idle Control System diagnostic observes engine speed in order to monitor the operation of the throttle actuator control (TAC) system. The powertrain control module (PCM) uses input from several engine sensors in order to determine the correct engine speed at idle. With the desired idle speed calculated, the PCM determines the correct throttle position (TP) needed to obtain the desired engine speed. The PCM sends the desired throttle position or target value to the TAC module. The TAC module achieves the desired throttle position by commanding the throttle control motor to position the throttle valve at the target value. If necessary, the PCM adjusts the target throttle position in order to achieve the desired engine idle speed.