U0025
Low Speed CAN Communication Bus (-) Low
Data bus (CAN)
Generic OBD-II
Medium
What it means
U0025 means a module has detected the negative CAN-Low wire of the low-speed data bus being pulled low — usually shorted toward ground. The low-speed bus mostly carries body and comfort messages, so a short on it can knock those modules offline and trigger a spread of warning lights.
Medium
Can I keep driving? Generally drivable, but body and comfort features on this bus may misbehave or stop and warning lights may appear; have it looked at before it spreads.
Common symptoms
What you'll notice
- Warning lights on, often several unrelated ones together
- Body/comfort features (locks, lighting, climate controls) glitching or dead
- Modules on the low-speed bus missing from a scan
- Several stored lost-communication U-codes
Common causes
Most likely first
- CAN-Low wire shorted to ground or to a chafe pointLikely
- Corroded or water-damaged connector on the low-speed busCommon
- A failed module dragging the bus voltage downCommon
- Damaged harness sectionLess often
- Poor ground shared with a bus moduleLess often
How to diagnose & fix
Work through it in order
- Read all module codes to see which section of the low-speed bus is down.
- Confirm battery voltage is good before chasing communication faults.
- Inspect low-speed CAN wiring for a short to ground — check chafe points and connectors.
- Measure bus resistance and voltage with the key off to spot a shorted leg.
- Unplug suspect modules one at a time; if the bus recovers, the last one disconnected is the culprit.
FAQ
Quick answers
Is it safe to drive with U0025?+
Usually yes, but the affected body/comfort features can quit without warning. If lights multiply or a system fails, get it diagnosed.
Can I just clear U0025?+
It will come back while the short is present. Repair the CAN-Low circuit first, then clear and retest.
Related codes
Often seen with U0025
Read & clear U0025 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