Different from the existing fixed cam phase angle type, CVVT(Continuously Variable Valve Timing) is the device which varies cam phase angle continuously to be optimum. And with engine oil pressure, it operates. CVVT consists of OCV(Oil Control Valve) and cam phaser. OCV, mounted on cylinder head, controlls the amount and direction of oil delivered to cam phaser by oil valve which is connected to a solenoid. Cam phaser, rotating cam phaser rotor with pressure and amount of oil produced by OCV, rotates cam shaft forcefully for or against the rotating direction and finally, cam shaft phase changes. With the appliance of CVVT, engine power,fuel efficiency and the quality of exhause gas are improved.

Tooth offsets are learned, updated, stored and initialized. For a given cam target wheel and systemcalibration, the tooth offsets should maintain relatively steady values. If the values of tooth offsets are observed to drift outside of an established range, then a failure is present for measuring cam phasing.

This diagnosis is to verify that learned tooth offsets are within an acceptable range.

PCM monitors tooth offset while no active faults is present.If the tooth offsets is out of threshold during more than 6 offset learning for 36 offset learning, PCM determines that a fault exists and a DTC is stored.