Invalid signals at the calibration interface
â–¶ How to fix
* Check the sealing (housing) of the tachograph. * If the error message appears repetitively, replace the tachograph.
What you'll see
No driver-visible symptom recorded.
System reaction
The interface is blocked and additional signals will be ignored until the entry of a PIN number is requested (workshop card is inserted). * Security breach warning message with error text "security breach" is diplayed in the tachograph display. * Event/ Fault EV401/MC27 is stored in the tachograph. * System event in TCO1 CAN message is set to active. * Tachograph warning (amber T) is displayed in the instrument cluster.
Diagnostic depth
Detection
Invalid signals detected on the calibration interface.
Possible cause
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