The VVT system used in all models include an intake camshaft timing that is controlled by oil pressure to either advance or retard the intake camshaft sprocket/actuator assembly for improvement of the engine power output, fuel economy, and reduction of emissions where these conditions prevail. They include the PCM, VVT oil control valve, the filter for the VVT oil control valve and the intake camshaft sprocket/actuator. Using a number of sensors, the PCM decides the oil control Valve to regulate the pressure of the oil to the actuator assembly. The actuator hydraulically driven contains an inner hub equipped with the fixed vanes and through the oil pressure the rotation of the camshaft is performed related to the adjustment through which the camshaft can be in advance to 21 degrees, or in case necessary-to be in a neutral state. Dependent on the load on the engine, the system can control the cam shaft timing in order to provide the right combustion. Especially, VVT oil control valve and the filter should be frequently maintained due to most problems root cause from them. To diagnose, the strainer of the oil control valve filter should be free from blockage, the valve's resistance would then be evaluated; if this has exceeded the allowable limit then it must be replaced. The second examination entails observing the movement of the plunger of the oil control valve every time voltage is supplied. As for the camshaft sprocket/actuator assembly, the valve cover and the camshaft have to be taken off; the actuator is then cleaned and it has to be installed correctly with the functionality as well. It is recommended to test the rotation of the actuator using air pressure and if it fails to do so, one must replace the assembly. Disassembly is the process of taking apart the equipment while reassembly is done systematically in a backward way to the process of disassembly.
