Network
generic / SAE
U0020
Low Speed CAN Communication Bus (+) Open
The CAN-High wire of a low-speed comfort bus (e.g. ISO 11898-3 / fault-tolerant CAN) is open. Single-wire fallback may keep some functions alive but a fault is logged because the bus is no longer fault-tolerant.
SystemNetwork
Typegeneric / SAE
GroupU0
Range / number– / 20
Possible causes
- CAN-High wire broken high
- Gateway module routing CAN messages incorrectly low
- CAN terminating resistor (120 Ω) drifted out of spec low
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
Inspection / repair
- Difficulty: hard
- DIY: shop recommended
- Estimated cost: 60–500 €
- Estimated time: 0.8–4 h
- Component: low speed can wiring
- Component: body control module
- MIL / check engine light
Sources
References
sae:J2012
iso:11898