1.13.2.3 Monitoring Function - Mechanical Chain Jump Diagnosis

P13BA, P13BB, P13BC, P13BD 

The diagnosis is executed after the reference position adaptation has been completed. The learned position of each camshaft signal edge is stored in the NVRAM of the ECU as an adaptation value. Before this value is stored, however, the new adapted value is compared to the old stored value. When the difference between them exceeds a maximum value, the error CAM_one_tooth_off is delivered to error management and the new value is not stored in NVRAM. A chain jump of the timing chain is detected with this diagnosis.

The mechanical chain jump diagnosis has an interface to the RBM Module.

1. In-Use Monitor Performance Ratio:

   The RBM Module increments the numerator and the denominator for the chain jump diagnosis. Like all monitors for which a standardized track and report in-use performance is required, the diagnosis monitor reports to the RBM Module via status flags.

2. Conditions for Incrementing the Numerator:

   The numerator is incremented only when stored faults do not inhibit the monitor and when the diagnostic has been executed and a fault could have been detected.

3. Conditions for Incrementing the Denominator:

   The denominator is incremented with every driving cycle.