Camshaft Diagnostics (CVVT)

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 of the camshaft from the 0 position. This is the extent to which the camshaft flanks are deviating from predetermined positions on the crankshaft (reference positions).
The position of the camshaft is stored in the control module as an adaptation 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 using VIDA.

Checking the camshaft control
When camshaft control is active, the control module checks that the camshaft moves to the intended position. This position ensures that the cam timing is correct so that the valves are opened and closed at the right time. This is done by measuring the time the system takes to deploy to the correct camshaft position (the transition time from the actual to the desired camshaft angle). 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. The function can be tested using VIDA.