U009CVehicle Communication Bus I Performance
- Generic OBD-II code · Network
- How the car detects it
- U009C reports that Vehicle Communication Bus I carries traffic, but not at the quality the module expects. U009C has not been documented in public by any manufacturer. The causes lie in signal integrity rather than a hard fault. Texas Instruments ties the possible bus length to the data rate, roughly 40 m when running at 1 Mbit/s and 100 m at half that rate, and names cable bandwidth and intersymbol interference as the limits; repairs with long added wire or untwisted cable eat into that margin. TI cites the standard's twisted pair with 120 ohms impedance. CAN detects such distortion as protocol errors: Wikipedia explains that after five identical bits the sender adds one of the inverse value, and six identical bits in a row count as an error, prompting a repeat.
- What you may notice
- Brief dropouts of functions on Bus I
- Delayed reactions of displays or controls
- Likely causes
- LikelyLoose contact causing bit errors
- PossibleRepair with untwisted or overly long wire
- RareMissing or wrong termination
- Repair
- Hard · Usually a job for a workshop.Typical cost: €50 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.