U0002High Speed CAN Communication Bus Performance
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- U0002 stands for impaired rather than lost traffic on the high-speed CAN, and makers fill the slot in different ways. GM/Saab sets it when a supervised periodic message, which also tells the receiver that its sender is alive, has not shown up within the 250 ms supervision time; the receiver then carries on with a default value. FCA calls U0002 CAN C Bus Off Performance: a reflash for the 2013 Ram 2500/3500 6.7 L diesel PCM changed it from a one-trip to a two-trip MIL fault, whereas the 2024-26 Dodge Charger steering column module stores it without MIL because dips in supply voltage lasting about 40 ms trip a software bug. In contrast to U0001 the bus mostly keeps working, so complaints come and go: sporadic warnings or single functions dropping out briefly.
- What you may notice
- Warning lamps that appear and disappear again
- Single functions briefly unavailable
- Code stored as history without a current fault
- Likely causes
- LikelyIntermittent contact at connectors or splices of the bus pair
- PossibleModule software reacting to short voltage dips (reflash available)
- PossibleWeak battery or poor ground causing brief module resets
- RareElectrical interference from retrofitted devices on the bus
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.