Camshaft Diagnostics (CVVT)

Camshaft diagnostics (CVVT)
In addition to the electrical check of the camshaft reset valve, the engine control module (ECM) checks that the camshaft position is correct and that the control (deployment and return phases of the cam timing) functions satisfactorily. The control module uses the signals from the camshaft position (CMP) sensor (camshaft position) and engine speed (RPM) sensor (crankshaft position) in the diagnosis.

Checking the camshaft position
The control module checks that the camshaft 0-position (mechanical rest position) is correct. At idle speed camshaft control is not activate. The control module checks the camshaft deviation from the 0 position, that is how much the camshaft flanks deviate from the predetermined positions on the crankshaft.
The camshaft position is stored in the control module as an adaptation value. The diagnostic trouble code (DTC) is stored in the engine control module (ECM) if the adaptation value is too high or too low. The adaptation value for the camshaft with camshaft control can be read off using VIDA.

Checking camshaft control
Active camshaft control checks that the camshaft assumes the position the control module intends the camshaft to move to, that is that the correct camshaft angle is obtained. This is done by measuring the time it takes for the system to reach the desired position (the time for the actual change position to reach the desired change position). A diagnostic trouble code (DTC) is stored in the Engine Control Module (ECM) if the cam timing does not reach the desired value within a specified time. The function can be tested using VIDA, quick test camshaft control.