Operation

With the valve timing solenoids de-energized, the coil springs in the bush carriers position the shuttle valves to connect the valve timing units to drain.
Within the VVT units, the return springs hold the pistons and gears in the retarded position.
When the timing solenoids are energized, the solenoid plungers position the shuttle valves to direct engine oil to the VVT units. In the units, the oil pressure overcomes the force of the return springs and moves the gears and ring pistons to the advanced position.
Maximum system response time: 1.0 second for advancing and 0.7 second for retarding.
With valve timing in the retarded mode, the ECM produces a periodic lubrication pulse once every 5 minutes. This momentarily energizes the valve timing solenoids to allow a spurt of oil into the VVT units.