The VTC oil control solenoid valve controls oil pressure to the advance chamber/retard chamber of the VTC actuator according to a signal from the ECM/PCM. When the VTC actuator vanes rotate to the advance or retard position, the intake camshaft timing is changed.

CMP sensor A detects the intake camshaft angle and sends the information to the ECM/PCM. The ECM/PCM controls the VTC oil control solenoid valve as the intake camshaft angle changes.