P1505 Buick Idle Air Control System At Adaptive Clip
– Idle Speed Control Actuator (ISCA) valve harness is open or shorted
– Idle Speed Control Actuator (ISCA) valve circuit poor electrical connection
The Idle Speed Control Actuator (ISCA) valve is installed on the intake manifold and controls the intake airflow that is bypassed around the throttle plate to keep constant engine speed when the throttle valve is closed. The function of the ISCA valve is to maintain idle speed according to various engine loads and conditions, and also to provide additional air during starting. The ISCA valve consists of an opening coil, a closing coil, and a permanent magnet. Based on information from various sensors, the ECM controls both coils by grounding their control circuits. According to the control signals from the ECM, the valve rotor rotates to control the by pass airflow into the engine.