U0025Low Speed CAN Communication Bus (-) Low
- Generic OBD-II code · Network
- How the car detects it
- U0025 flags CAN-Low pulled toward ground on a low-speed CAN with two conductors. In the fault-tolerant physical layer of ISO 11898-3 CAN-Low idles near 5 V, so a ground short forces it into its dominant state for good. NXP's TJA1055 (failure 4) first sees a permanently dominant receive signal; after about 0.3 to 1.6 ms it switches the CAN-Low driver off, changes that line's termination to a weak pull-up and continues in single-wire mode on CAN-High. Messages keep flowing, but with weaker immunity to interference, so sporadic dropouts of comfort functions are possible. The transceiver goes back to differential mode by itself once the short is gone. No manufacturer documents U0025 publicly; GM's one-conductor bus has no (-) side at all. Resistance from CAN-Low to ground near 0 Ω with the battery off confirms the fault.
- What you may notice
- Comfort functions work but drop out now and then
- Body modules store the code repeatedly
- Likely causes
- LikelyCAN-Low insulation damaged and touching body ground
- PossibleHarness trapped by a panel, bracket or seat mechanism
- RareModule transceiver internally shorting CAN-Low to ground
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.