U0018Medium Speed CAN Communication Bus (-) Shorted to Bus (+)
- Generic OBD-II code · Network
- How the car detects it
- U0018 describes the two medium-speed CAN lines, CAN-Low and CAN-High, shorted together. With no voltage difference left, receivers see only recessive bits, nobody can win arbitration, and the controllers on the segment eventually go bus-off; onsemi's measurements on the comparable high-speed layer show transmission stopping completely. NXP notes that transceiver diagnosis does not catch this short, so it is inferred from protocol errors. No manufacturer documents U0018 publicly. Expect the complete comfort network to fail together while the powertrain bus stays unaffected. With the battery disconnected, a near-zero resistance between (+) and (-) in place of the normal termination value confirms it; separating connectors section by section narrows the location, often a crushed or wet harness.
- What you may notice
- Entire comfort network fails, powertrain unaffected
- Body modules unreachable with the scan tool
- Likely causes
- LikelyMedium-speed bus pair crushed so both wires touch
- PossibleWater in a connector bridging (+) and (-)
- RareFailed transceiver shorting both bus pins in a comfort module
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.