Camshaft Reset Valve, Controlling
- Oil filter reset valve camshaft.
- Oil channel (pressure, inlet).
- Channel connected with CVVT-unit's chamber (triggering).
- Channel connected with CVVT-unit's chamber (re-triggering).
The camshaft reset valve controls the oil flow to the continuous variable valve timing (CVVT) unit. The Engine Control Module (ECM) uses a Pulse Width Modulation (PWM) signal to control the valve. See also INTAKE CAMSHAFT CONTROL VALVE and EXHAUST CAMSHAFT CONTROL VALVE .
The Continuous Variable Valve Timing (CVVT) unit allows the position of the camshaft to be adjusted relative to the crankshaft.
The camshaft is secured to the CVVT-unit's rotor. The rotor (and thus, the camshaft) can rotate in relation to the timing belt pulley by the oil pressure building up on one or the other side of the rotor's vanes in the CVVT-unit.
Control occurs according to the following during deployment/return of the camshaft.
A: Inlet camshaft
- Oil pressure from the lubrication system (1) of the engine.
- The oil passes the filter for the camshaft reset valve (2) and then on to the reset valve (3).
- The Engine Control Module (ECM) controls the oil flow to one of the CVVT unit chambers (4) depending on whether it is to be deployed/returned by the camshaft.
The reset valve is controlled by the Engine Control Module (ECM) by high frequency, switching for deployment and return. This results in rapid and precise control. The camshafts can be triggered up to approx. 40 crankshaft degrees.
Camshaft diagnostics (CVVT)
In addition to electrical checks of the camshaft reset valve, the Engine Control Module (ECM) checks that the position of the camshaft is correct and that the control (deployment and return of the camshaft) is working satisfactorily. The control module uses the signals from the camshaft position sensor and engine speed (RPM) sensor (crankshaft position) for the diagnostics.
Checking the camshaft position
The control module checks that the 0 position of the camshaft (mechanical rest position) is correct. During certain driving conditions, camshaft control is not active. If this is the case, the control module checks the deviation between the camshaft position (angle position) and the crankshaft position (angle position).
The difference is stored in the Engine Control Module (ECM) as an adaption value. A Diagnostic Trouble Code (DTC) is stored in the Engine Control Module (ECM) if the adaptation value becomes too high or low. The deviation of the camshafts from the reference position can be read off.
Checking the camshaft control
When camshaft control is active, the control module checks that the camshaft moves to the intended position. If the position is not reached, the time the system takes to deploy to the correct camshaft position (the transition time from the actual to the desired camshaft angle) is measured. A Diagnostic Trouble Code (DTC) is stored in the Engine Control Module (ECM) if the camshaft angle does not reach the desired value within a certain time frame.