CAN network: Compatibility

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The units must "speak" the same language and must be compatible with each other. A standardized communication protocol is used for this.

Signal configuration (sfg) contains the language between the units. If any module has a signal configuration which does not correspond to other units the module cannot communicate. This means that all the units must have compatible signal configuration.

To check this the central electronic module (CEM) transmits an identification number for its signal configuration over the controller area network (CAN). The other control modules receive this number and compare it with their own. If this identity does not correspond the control modules store a diagnostic trouble code (DTC) (XXX-E003). The signal configuration is occasionally modified so that the new messages are added and old messages removed.