Medium Speed CAN Communication Bus (+) Low
What it means
U0013 means the voltage on the medium-speed CAN "high" (+) wire has fallen below the expected range. This is the network many body and comfort modules use to talk to each other, so when its voltage is pulled low they can't share data reliably — usually from a wiring short, a bad connector, or a module dragging the bus down. Expect warning lights and dropped features rather than a dead engine.
Can I keep driving? Usually yes — the engine typically still runs, but expect warning lights and dropped features on the affected network; have the bus fault traced before more modules fall offline.
Common symptoms
What you'll notice
- Warning lights on (check-engine, ABS, airbag or others depending on what shares the bus)
- Features on the medium-speed network drop out (climate, body electronics, driver displays)
- Intermittent gauge, message-center or accessory glitches
- Several unrelated communication codes stored across different modules
Common causes
Most likely first
- CAN-high (+) wire shorted to ground or to a lower-voltage circuitLikely
- Chafed, pinched, or corroded bus wiring or a bad connectorCommon
- A failing module pulling the bus voltage downCommon
- Poor power or ground feed to a networked moduleLess often
- Water intrusion in a connector or moduleLess often
How to diagnose & fix
Work through it in order
- Scan every module and record all stored codes — the pattern shows which branch of the bus is affected.
- Inspect the medium-speed CAN wiring and connectors for chafing, corrosion, or moisture.
- Measure CAN-high/low voltage and resistance against spec to locate the short-to-low.
- Disconnect suspect modules one at a time to find one dragging the bus down.
- Repair the wiring or replace the faulty module, then clear the code and re-test.
FAQ
Quick answers
Is it safe to drive with U0013?+
Can I just clear U0013?+
Related codes
Often seen with U0013
Read & clear U0013 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.