Camshaft Diagnostics

Camshaft diagnostics

The task of the variable camshaft is to alter the camshaft position to minimize emissions and optimize the engine performance. The camshaft displacement in relation to the crankshaft is calculated using the engine load and engine speed (RPM).
The exhaust camshaft is variable, the intake camshaft has a set position in relation to the crankshaft.

The diagnostic consists of 4 components:
1. When the when the ignition is switched on an electrical check is carried out on the signal cable, the power supply cable and the solenoid. The check is carried out for a short-circuit to supply voltage/ground and open-circuit. With the engine running this diagnostic is switched off.
2. The camshaft position is checked in comparison to the flywheel, when the camshaft is in its 0-position (mechanical resting position). If the deviation is excessive the variable camshaft is switched off.
3. In case of larger controlled deviations at the variable camshaft the time taken to regulate to the control value is measured. This time is used partially to determine how long it takes to alter the camshaft angle and partially to switch off the variable camshaft if the time exceeds a certain maximum time. The information about the speed of the camshaft angle change is used in the control strategy. The camshaft uses the engine oil and oil pressure to turn. The turning time depends on oil pressure, viscosity etc. which in turn depends on oil temperature and quality etc.
4. The camshaft position (CMP) sensor is compared with the flywheel sensor to check if the camshaft position (CMP) sensor detects all lobes.

Mechanical 0 position:
For turbocharged engines the camshaft mechanical 0-position is in the performance position.