U0071
Vehicle Communication Bus A (+) Bus Off
The CAN controller for bus A has shut its plus driver after exceeding the SAE J2284 / ISO 11898 transmit error threshold. The node disconnects from the bus until error counters recover.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
Ordered by how often each turns out to be the cause.
- Persistent short on the CAN-H wireCommon
- One module driving bus permanently dominantPossible
- Gateway module routing CAN messages incorrectlyLess likely
Parts involved
- CAN Transceiver
- CAN High Wire
U0071 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.