Bus Off

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📖 YOUCANIC Automotive Glossary

Bus Off is a critical CAN error state where a module has detected so many consecutive errors that it disconnects from the network to prevent corrupting communication for all other modules. CAN includes error management with Transmit and Receive Error Counters in each module — when the Transmit Error Counter exceeds 255, the module enters Bus Off, stopping all transmit and receive. This self-isolation prevents one malfunctioning module from crashing the entire network.

A Bus Off module causes loss of its functions plus U-code errors in every module expecting data from it. Common causes: damaged CAN wiring, failing module generating corrupted messages, electromagnetic interference from aftermarket electronics, and corroded CAN connector pins. Diagnosis involves checking voltage levels, measuring termination resistance, and systematically disconnecting modules to isolate the source.

Synonyms:
CAN Bus Off, Bus Off Error
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