Variable Valve Timing (VVT and VVT-i) system — description
1. The VVT system varies intake or exhaust camshaft timing by directing oil pressure to advance or retard the camshaft sprocket/ actuator assembly. Changing the camshaft timing during certain engine conditions increases engine power output, fuel economy and reduces emissions.
2. System components include the Powertrain Control Module (PCM), the VVT oil control valve (OCV) and the intake camshaft sprocket/actuator assembly on all models and the exhaust camshaft on 2010 and later models (see illustrations).
5.2a on 2009 and earlier models, the Variable Valve Timing (VVT) oil control valve is located at the rear of the cylinder
5.2b on 2010 and later models, there are two Variable Valve Timing (VVT) oil control valves located in the valve cover
A Intake camshaft VVT oil control valve
B Exhaust camshaft VVT oil control valve
3. The PCM uses inputs from the following sensors to turn the oil control valve ON or OFF:
- ) Vehicle Speed Sensor (VSS)
- ) Throttle Position Sensor (TPS)
- ) Mass Airflow (MAF) sensor
- ) Engine Coolant Temperature (ECT) sensor
4. Once the VVT oil control valve is actuated by the PCM, it directs the specified amount of oil pressure from the engine to advance or retard the intake or exhaust camshaft sprocket/actuator assembly (see illustrations).
5.4a Location of the intake camshaft actuator assembly on 2009 and earlier models
5.4b Locations of the intake (A) and exhaust (B) camshaft actuators on 2010 and later models
5. The camshaft sprocket/actuator assembly is equipped with an inner hub that is attached to the camshaft. The inner hub consists of a series of fixed vanes that use oil pressure as a wedge against the vanes to rotate the camshaft. The higher the oil pressure (or flow), the more the actuator assembly will rotate, thereby advancing or retarding the camshaft.
6. When oil is applied to the advance or retard side of the vanes, the actuator can advance or retard the camshaft timing. The PCM can also send a signal to the oil control valve to stop oil flow to both (advance and retard) passages to hold camshaft(s) in its current position.