A car equipped with the 2012 GMECOTEC 1.8L engine of the general motors. The owner reflects: the engine fault indicator light of the vehicle is lit, and the engine is often turned off for no reason. After receiving the vehicle, the RIDS diagnostic tool is used to enter the engine control module to read the fault code. It is found that there are two fault codes of the P0026 intake VCP hydraulic control valve and the P0012 intake VCP cam phase error in the engine control module. The intake cam position data flow is read. It is found that the variable phase angle of the intake cam has been kept 0, and the variable phase of the intake cam changes between 3~38 degrees when the normal vehicle is running. It is initially suspected that the intake cam variable phase actuator is stuck at the initial position (0 position). The engine control module changes the internal oil pressure flow and direction in the intake cam variable phase actuator by controlling the current of the intake cam solenoid valve coil, and may cause the hysteresis of the solenoid valve or the stagnation of the phase actuator. The resistance value of solenoid valve coil measured by multimeter is 8.9 ohms, within normal range. Measure the terminal voltage of two terminals and change the voltage range from 4 to 5.5V at idle speed. This voltage is consistent with other normal engines. It is doubted that the solenoid valve is stuck in the oil circuit, and the intake is the same as that of the solenoid valve parts. The intake cam solenoid valve and the exhaust cam solenoid valve are interchanged, and the angle of the variable phase actuator of the intake cam remains unchanged at 0. The fault may be the stagnation of the variable phase actuator itself. After changing the variable phase actuator of the intake cam, the angle of the intake cam is changed and the test fault is ruled out. It is particularly noted that the variable phase actuator of the engine intake cam is integrated with the intake camshaft gear, and should be replaced with the gear, the camshaft gear and the camshaft of the engine have no positioning pin assembly, so it is necessary to use a special tool to locate the camshaft gear on the camshaft. . Replace the intake cam variable phase actuator after troubleshooting.