U0011: CAN-Kommunikationsbus Medium-Speed — Funktion
Was zu tun ist
Everything probably works, and this is still worth attending to. That is the whole point of this page.
Your car's internal network is running, but messages are arriving corrupted and having to be sent again. The system is good enough at recovering that you notice nothing at all — which is exactly why this gets ignored.
Read it as an early warning. A connector corroding but still conducting, a wire down to its last few strands, insulation nearly rubbed through — all of those cause errors for a long time before they cause a failure. This is that stage.
And there is a practical reason to act now. The fault is present today, which is the easiest possible condition to measure. Once it becomes intermittent, it is one of the most expensive things on a car to chase — it produces a flood of unrelated fault codes and then clears before anyone can look.
One question is worth answering: has anything been added to the car? A tracker, dashcam, insurance box, alarm, stereo or tow bar. Anything spliced into the network changes its electrical behaviour, and a long tail of cable to an added device is a well-known cause of exactly this — invisible at rest, and visible only as errors.
Mention any damp carpets or wet boot floor while you are at it.
Was dieser Code bedeutet
The medium speed data bus is working, and not working properly. See U0010 for what this network is and U0003 for the electrical faults.
This is the most useful code in the whole range and the one most likely to be dismissed, because everything still works.
A performance code is not a failure report. It is an error rate. Messages are arriving corrupted and being retransmitted, frames are being rejected, and the bus is spending part of its time correcting itself instead of carrying traffic. CAN is good enough at recovering that a driver notices nothing — which is exactly why this deserves attention.
So the right way to read it is as an early warning. The faults at U0012 to U0018 are the same problems after they finished developing. A connector corroding but still conducting, a conductor with three strands left, insulation nearly through, a terminator drifting out of value — each produces errors long before it produces silence.
And the practical argument for acting now rather than later: the fault is currently present, which is the hardest condition to arrange on purpose. A workshop can measure a degraded bus today. Once it fails intermittently, they cannot — and an intermittent bus fault is one of the most expensive things to chase on a vehicle, because it produces a flood of unrelated codes and then clears.
Two causes belong specifically to a degraded rather than broken bus.
Something added to the network. A device spliced onto the pair changes its electrical characteristics — the bus is a terminated transmission line rather than a wire — and a long stub of cable to an aftermarket module reflects signals back down it. That is invisible at rest and shows up only as errors.
And a marginal connection somewhere. The bus tolerates one poor joint and reports it as errors; it stops at the second.
Wahrscheinliche Ursachen
Hier anfangen
- Schlechte Leitungsverbindung in einem nachträglichen Einbau · mittel
- Korrodierter oder loser Stecker · einfach
- Datenbusleitungen beschädigt · mittel
- Wasser in den Stecker eingedrungen · mittel
Seltener
- Busabschlusswiderstand defekt · Fachwerkstatt
- Zeitweiliger Fehler in der Verkabelung · mittel
Symptome
Beteiligte Bauteile
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