Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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.: Digital Diesel Electronics) detects on the basis of the substitute value that the bus communication is OK. The function of the DDE, however, might be restricted and for this reason a signal fault is stored in the DDE.
If signal faults are detected, they are assigned to the causing control unit. Troubleshooting is then to be continued in the sending control unit.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.