Signals in message invalid: Notes

In the control unit network, important information is transferred across the bus for the function of the control unit:

• Message fault

  are stored if the communication across the bus (e.g.: CAN bus) is disrupted (e.g.: timeout).

• Signal fault

  are stored when communication across the CAN bus is generally OK, but the transmitting control unit cannot send a value and therefore sends a substitute value (default value).

  Example:

  The DSC can only send a valid speed signal for a wheel speed sensor if this is OK. If the wheel speed sensor is not OK, the DSC sends a defined substitute value (default value). The receiving control unit (e.g.: DME) detects on the basis of the substitute value that the bus communication is OK. The function of the DME, however, might be restricted and for this reason a signal fault is stored in the DME.

If signal faults are detected, they are assigned to the causing control unit. Troubleshooting is then to be continued in the sending control unit.