Faulty Idle Air Control Valve
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)
Engine rough idle
The target idle speed is in the Engine Control Module (ECM) memory for various engine conditions (coolant temperature, A/C operation and so on). 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. If the IACV output duty cycle (the length of ON time) is out of a specified range, a malfunction is detected and a DTC is stored.