Faulty Idle Air Control Valve (IACV)
Idle Air Control Valve harness is open or shorted
Idle Air Control Valve circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
The target idle speed is in the Engine Control Module (ECM) memory for various engine conditions (coolant temperature, A/C operation, and other functions). The ECM keeps the actual idle speed at the target idle speed by switching the Idle Air Control Valve (IACV) ON/OFF to control the intake airflow. In addition, the IACV functions as the first idle valve to control the actual speed according to the engine coolant temperature. If the duty cycle signals are not inputted to a circuit that checks return signals in the ECM, a malfunction is detected, and the P1519 code is stored.