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PCM controls OCV(Oil Contol Valve) with PWM (Pulse Width Modulator) signal to change oil passages supplying oil to CVVT that makes CAM postion changes (advance or retard). OCV is integrated with oil filter and located at the nearest CVVT on the engine block.

The oil control valve is commanded by a pulse-width-modulated signal from the engine control unit. A duty cycle of zero commands the cam phaser to its default position. A duty cycle of 100% commands the phaser to its maximum phased position. When the phaser must be controlled to an intermediate position, the duty cycle is maintained in the region of the ‘hold position’. This is a medium duty cycle, usually between 35% and 65%, depending on temperature and voltage conditions. As the cam phaser is advanced and retarded, its position is measured using a toothed wheel.

The wheel is attached to the camshaft, or to the cam phaser rotor. A sensor picks up the signal from the wheel and its output is read by the engine control unit. A cam signal is generated for each cam phaser on the engine. This requires a separate toothed wheel and cam sensor combination for each cam phaser. The cam signal and crankwheel signal are compared as the engine turns, and the phasing position is determined. The position is displayed in crank angle degrees, relative position from default. This position measurement is used as feedback for the position control software, which determines the required percent duty cycle commanded to the oil control valve.

When ECM detects open in the OCV control circuit, ECM sets DTC P0075.