U0051
Vehicle Communication Bus C (-) Open
Communication network (CAN bus)
Generic OBD-II
Medium
What it means
U0051 means a module has detected an open circuit on the CAN-Low (-) wire of communication bus C. With the CAN-Low line broken, modules past the break can't exchange data, so you typically see several lost-communication codes and dead features rather than an engine fault. It's a wiring-side problem: a broken wire, backed-out pin, or corroded connector on the CAN-Low side.
Medium
Can I keep driving? Usually drivable to get it repaired, but an open bus wire can silence whichever modules sit past the break and trip several warning lights.
Common symptoms
What you'll notice
- Several modules on bus C reporting lost communication
- Warning lights and dead features tied to those modules
- Fault appears after wiring work, rodent damage, or a collision
- Intermittent operation that changes with wiring movement
Common causes
Most likely first
- Open (broken) CAN-Low (-) wire on bus CLikely
- Disconnected or backed-out connector terminalCommon
- Corroded or damaged wiring between modulesCommon
- Internal open in a module's CAN-Low connectionLess often
How to diagnose & fix
Work through it in order
- Scan all modules; the group that dropped off marks the open segment of bus C.
- Inspect the bus C CAN-Low wiring and connectors for breaks, backed-out pins, and corrosion.
- Measure continuity along the CAN-Low line to pinpoint the open.
- Repair the broken wire or reseat/replace the faulty terminal.
- Clear the code and confirm the affected modules return online.
FAQ
Quick answers
Is it safe to drive with U0051?+
Usually yes to reach a repair — bus 'C' is typically not the core engine bus. But an open wire can disable safety-adjacent features, so don't put the fix off.
Can I just clear U0051?+
No — an open circuit is a physical break. The code comes back until the wire or connector is repaired.
Related codes
Often seen with U0051
Read & clear U0051 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX