Variable Camshaft Timing (VCT) Control

The inlet camshaft is controlled by the ECM using the VCT solenoid. The exhaust camshaft is fixed and its timing cannot be changed.

Both camshafts are driven indirectly from the crankshaft via a chain. The chain is driven from a shaft in the gear housing assembly. Refer to ENGINE (I6 3.2L PETROL) . The VCT allows the ECM to adjust the inlet camshaft position in relation to the crankshaft, altering the timing of the opening and closing of the inlet and exhaust valves relative to the crankshaft position. This allows the ECM to provide increased engine performance, improved idle quality and reduced emissions.

The position of the inlet camshaft is determined by the ECM using signals from the CKP sensor and the CMP sensors. The ECM can then use the VCT solenoid valve to control the angle of the camshaft by controlling the flow of oil to the VCT unit.

The camshaft is secured to the rotor in the VCT unit. Oil pressure supplied to either side of the VCT unit from the VCT solenoid valve can rotate the rotor and hence the camshaft in either direction. The VCT solenoid is operated by the ECM using PWM, high frequency switching which provides rapid and precise control of the inlet camshaft position. The inlet camshaft position can be adjusted within 40 degrees of crankshaft rotation.