Time Master
The Time Master is located in the instrument panel and cyclically transmits the system time to all other control units in the vehicle every second.
This system time is set to zero only once in the life cycle of the vehicle while in the factory at the end of the production process. The system time expresses the time in seconds that have passed since initialization in the factory.
The counter for the system time is not reset when the battery is disconnected or when the power to the instrument panel is switched off.
When the battery is disconnected the time value is actually initially lost, but it is updated when the power supply is again available. This is achieved by reading the last value stored in the non-volatile memory (EEPROM), increasing it by one time unit, and applying it in the Time Master as a new system time. The counter for the system time can map a time of approximately 136 years.
The system time is received by all control units, and used it as a time stamp when fault messages are stored.
To allow retention of the system time even after replacement of the instrument panel, it is stored redundantly in the CAS similar to the mileage reading.