U0008
High Speed CAN Communication Bus (-) High
The CAN-Low signal is held above its valid range, typically because of a short to battery voltage on the CAN-L wire. Bus communication is lost for every node sharing this segment.
- 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 shorted to battery voltageCommon
- Chafed harness against power wirePossible
- Gateway module routing CAN messages incorrectlyLess likely
Parts involved
- CAN Low Wire
- Module Connector
U0008 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.