Circuit Description

WARNING: This page is about a different car, the 2003 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.

The VVT system controls the intake camshaft to provide the optimal valve timing for every driving condition. This control is performed based on the signals and such conditions as intake air volume, throttle position and engine coolant temperature. The ECM controls the oil control valve (OCV), based on the signals output from the sensors. The VVT controller regulates the intake camshaft angle using oil pressure through the OCV. As a result, the relative position between the camshaft and the crankshaft becomes optimal, and the engine torque improves, fuel economy improves, and exhaust emissions decrease under overall driving conditions. Also, the ECM detects the actual valve timing using the signals from the camshaft position sensor and the crankshaft position sensor, and performs feedback control. This is how target valve timing is achieved by the ECM. DTC is detected when there is an open or short in oil control valve circuit. See Figure and Figure . Possible causes are:

Faulty valve timing.
Faulty OCV.
Faulty VVT controller assembly.
Faulty ECM.