U0045Vehicle Communication Bus B (-) Shorted to Bus B (+)
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U0045 describes the two wires of Vehicle Communication Bus B touching each other. Deutz uses this code in the EMR L1 engine controller for a short circuit on its third CAN channel, without further detail. On a high-speed-type CAN, bridged wires leave no differential voltage, every bit reads recessive and, per onsemi, nothing can be transmitted while the CANH driver works into its current limit; NXP adds that transceiver diagnosis cannot see this short. On a fault-tolerant low-speed network, NXP's TJA1055 first sees a permanent dominant level, then after a time-out switches off CAN-Low and keeps going on CAN-High. Typical causes are crushed harness sections, water in splices and a damaged module input. No car maker documents U0045 publicly; near-zero ohms between the wires with the battery off confirms the fault.
- What you may notice
- Every function on Bus B unavailable (high-speed type)
- Several warning lamps on at once
- Lost-communication codes in modules on other networks
- Likely causes
- LikelyHarness crushed so that both bus wires touch
- PossibleWater in a splice or connector bridging the two wires
- RareDamaged module input shorting its bus pins
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.