Camshaft Reset Valve (Continuous Variable Valve Timing (CVVT))

Fig 1: Camshaft Reset Valve

Courtesy of VOLVO CARS OF NORTH AMERICA.

The camshaft reset valve controls the oil flow to the continuous variable valve timing (CVVT) unit.

The valve consists of an electro-magnetic valve with a spring-loaded piston. There are slits in the piston which channel the engine lubricating oil to different channels in the continuous variable valve timing (CVVT) unit by moving the piston in the reset valve. The continuous variable valve timing (CVVT) unit turns the camshaft (the cam timing changes). The direction in which the camshaft turns depends on the chamber in the CVVT unit which is supplied with oil (pressure).

See also Camshaft control (CVVT) 

The system relay supplies the reset valve with voltage. The valve is grounded (control stage) in the engine control module (ECM). When the valve is grounded using a pulse width modulation (PWM) signal, the oil flow in the valve can be regulated to the different chambers in the continuous variable valve timing (CVVT) unit at variable rates. This allows the cam timing to be changed precisely and steplessly.

The engine control module (ECM) can diagnose the camshaft reset valve. The value of the reset valve can be read using appropriate diagnostics tool.

The valve is on the cylinder head above the camshaft with CVVT (certain markets have CVVT on both the intake and exhaust camshafts).