U0071Vehicle Communication Bus E (-) High
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- With U0071 the (-) conductor of Vehicle Communication Bus E sits too high, mostly by a short to battery voltage. Where Bus E is a high-speed CAN this is CAN-Low, and the bus dies: the line can no longer be pulled down, onsemi's node failed every start of frame, and NXP's TJA1041 note lists CAN-Low at battery or at 5 V as faults that prevent any communication. All Bus E modules drop out, and the gateway or other networks log them as lost. A fault-tolerant low-speed transceiver reacts differently; NXP's TJA1055 detects CAN-Low at battery voltage after a filter delay, turns its CAN-Low output off and receives via CAN-High alone. No manufacturer documents U0071 publicly. With ignition on, a CAN-Low reading at battery level rather than in the 1.5-2.5 V band confirms it.
- What you may notice
- All functions on Bus E fail together (high-speed type)
- Gateway or other modules report lost communication
- Likely causes
- Likely(-) wire of Bus E chafed against a battery or ignition feed
- PossibleWater in a connector linking the (-) wire to a supply pin
- RareDamaged transceiver driving the (-) line high
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.