1.13.7 Monitoring function - VVL control unit faults

P1041/P1044, P1042/P1045, P1043/P1046, P1071/P1072 

Faults in the control unit are distinguished between memory bit errors (RAM, ROM and EEPROM) and detectable hardware problems.

RAM faults are checked at the very beginning of the program and in normal operating mode via complements checks of critical values.

The ROM diagnosis calculates a CRC checksum continuously at normal operation.

EEPROM faults are detected within the adaptation routine or with a plausibility check of trim values at system start. The adaptation values are written into the EEPROM at the end of the adaptation routine with their complement values. The trim values are written at hardware checks within end-of-line tests at the VVL-ECU production and stored with their complement values redundantly as well.

Detectable hardware problems are:

1. Temperature sensor voltage is below 0.98 V or the absolute value of the gradient of the temperature sensor voltage is greater than 0.18 V.
2. A defect watchdog circuit.

Error Symptoms: