U0022Low Speed CAN Communication Bus (+) Low
- Generic OBD-II code · Network
- How the car detects it
- U0022 indicates a ground short on CAN-High, the positive conductor of a dual-wire low-speed CAN. In the fault-tolerant design of ISO 11898-3, where CAN-High idles at about 0 V and only rises for dominant bits, a ground short simply takes that rise away. NXP's TJA1055 lists CAN-High to ground as failure 5 and keeps transmitting and receiving differentially, since its receiver threshold is chosen so that reception stays correct in this case as well. The network therefore keeps working, and the driver often notices nothing apart from the stored code. On GM's single-wire low-speed GMLAN the (+)/(-) naming does not fit. No manufacturer documents U0022 publicly. With the battery disconnected, a reading near zero ohms from CAN-High to ground confirms the short; trim screws and seat rails are typical culprits.
- What you may notice
- Frequently no symptom besides the stored code
- Rare sporadic comfort function faults
- Likely causes
- LikelyCAN-High insulation chafed through against body ground
- PossibleWire pierced by a trim screw or trapped under a seat rail
- RareInternal transceiver fault pulling CAN-High low
- 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.