U0011
Medium Speed CAN Communication Bus Performance
Communication network (CAN bus)
Generic OBD-II
Medium
What it means
U0011 is a network code: a module has detected that the medium-speed CAN bus — the data line that links body and comfort modules — is not communicating reliably. The bus is present but the data is intermittent or corrupted, usually from wiring, a bad connector, or one module dragging the network down. The engine typically still runs, but expect warning lights and glitchy body features until it's fixed.
Medium
Can I keep driving? Usually drivable — the engine still runs, but expect warning lights and some body or comfort features to act up until the bus fault is fixed.
Common symptoms
What you'll notice
- One or more warning lights on the dash
- Body/comfort features glitch or stop working (climate, lighting, infotainment, windows)
- Multiple modules set communication codes at once
- Intermittent faults that come and go with vibration or temperature
Common causes
Most likely first
- Corroded or loose connector on the medium-speed CAN circuitLikely
- Chafed, pinched, or broken CAN wiring between modulesCommon
- A single failing module loading down or corrupting the busCommon
- Water intrusion into a connector or moduleLess often
- Failed bus terminating resistorLess often
How to diagnose & fix
Work through it in order
- Scan all modules and note every code — the pattern shows which segment of the bus is affected.
- Inspect medium-speed CAN connectors and wiring for corrosion, chafing, and moisture.
- Check CAN-High/CAN-Low resistance and voltages against spec to find opens or shorts.
- Disconnect suspect modules one at a time to see if the bus recovers, isolating a failed module.
- Repair the wiring or replace the faulty module, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with U0011?+
Usually yes for short trips — the medium-speed bus carries body and comfort data, not core engine control, so the car still runs. But fix it promptly, since a failing bus can knock out safety-related features too.
Can I just clear U0011?+
It will clear, but if the wiring or module fault is still present it returns quickly. This is a network fault that needs the physical cause repaired.
Related codes
Often seen with U0011
Read & clear U0011 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