U0043Vehicle Communication Bus B (-) Low
- Generic OBD-II code · Network
- How the car detects it
- U0043 reports the (-) line of Vehicle Communication Bus B shorted toward ground. Where Bus B is built like a high-speed CAN, that line is CAN-Low, and the fault is sneaky: onsemi measured frames still getting through, with distorted levels and the node drawing about 72 mA instead of 65 mA, because the CANH driver now pushes current through the termination into ground. NXP lists the case among hidden failures. NXP's fault-tolerant TJA1055 transceiver instead detects the short, switches off its CAN-Low driver and carries on single-wire over CAN-High. In both cases the vehicle tends to run normally, with the code logged by one module or showing up only now and then, which sets it apart from U0040, where the bus goes quiet. No manufacturer documents U0043 publicly; near-zero ohms from CAN-Low to ground confirms it.
- What you may notice
- Vehicle mostly normal, code stored by a single module
- Occasional communication errors
- Likely causes
- Likely(-) wire insulation damaged and touching ground
- PossibleHarness trapped under a panel or bracket
- RareFaulty transceiver pulling the (-) line to ground
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.