U0027Low Speed CAN Communication Bus (-) Shorted to Bus (+)
- Generic OBD-II code · Network
- How the car detects it
- U0027 describes the two wires of a low-speed CAN, (+) and (-), touching each other. On a high-speed bus such a short ends all traffic, but the fault-tolerant layer of ISO 11898-3 is built to ride it out. NXP's TJA1055 counts it as failure 7: the receive signal first sticks at dominant, then within about 0.3 to 1.6 ms the transceiver turns off its CAN-Low driver, leaves that wire with only a weak pull-up and carries on in single-wire mode. Comfort functions usually still work, though with less margin against interference, and differential operation resumes by itself once the short is cleared. No manufacturer documents U0027 publicly; a single-wire bus like GM's low-speed GMLAN cannot have this fault at all. Squeezed harness sections and wet splices are the likely spots; compare the high-speed sibling U0009.
- What you may notice
- Comfort network keeps running, sometimes with dropouts
- Higher sensitivity to electrical interference
- Code stored in several body modules at once
- Likely causes
- LikelyHarness crushed so that both bus wires make contact
- PossibleWater in a splice or connector bridging the two wires
- RareDamaged transceiver bridging its two bus pins
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.