U009BVehicle Communication Bus I
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U009B addresses Vehicle Communication Bus I overall, the ninth network letter. Which network sits behind I is left to the manufacturer and not named in any public bulletin; U009B itself is not documented publicly by any maker. CARB requires that a lost digital input be detected with a separate code, which is the role of this group. Bus I has no wire-level codes of its own in the list, so U009B must also cover line faults. One cause is easy to overlook: a single module with a fault in its controller can hold the bus dominant. NXP's TJA1042 and TJA1051 transceivers counter this with a time-out that switches off the transmitter, so that the remaining nodes keep talking. Unplugging modules one by one finds such a node.
- What you may notice
- Functions of Bus I modules fail or act erratically
- Lost-communication codes in several modules
- Likely causes
- LikelyOpen or shorted wire on Bus I
- PossibleOne module holding the bus dominant
- PossibleMissing supply or ground at a Bus I module
- Repair
- Hard · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.