U0009High Speed CAN Communication Bus (-) Shorted to Bus (+)
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U0009 describes CAN-Low and CAN-High of the high-speed bus being shorted to each other. The voltage difference between them then stays at zero, which every receiver interprets as recessive, so a dominant bit can never form; onsemi's tests show transmission stopping entirely and controllers running into bus-off. According to NXP, transceiver bus diagnosis cannot detect this short, so a module infers it from protocol errors instead. No manufacturer documents U0009 publicly. With the battery disconnected, the resistance between both lines reads close to zero ohms instead of the usual 60. Likely sources are a crushed harness section, water inside a splice or connector, or a damaged transceiver in one module bridging its two bus pins. Unplugging modules one by one narrows the location down.
- What you may notice
- No communication on the high-speed network at all
- Numerous warnings, fallback modes, possibly no start
- Scan tool reaches only modules on other networks
- Likely causes
- LikelyBus pair crushed so that both conductors touch
- PossibleWater or corrosion bridging CAN-High and CAN-Low in a splice or connector
- RareFailed transceiver shorting both bus pins inside a module
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.