U0012
Medium Speed CAN Communication Bus (-) Open
The CAN-Low wire on the medium-speed comfort/body bus is open. Body modules such as door modules, climate control or seat modules lose communication, but powertrain functions usually stay alive.
- 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.
- CAN-Low wire broken in body harnessCommon
- Loose body control module connectorPossible
- Gateway module routing CAN messages incorrectlyLess likely
Parts involved
- CAN Low Wire
- Body Control Module
U0012 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.