U0001: CAN-Kommunikationsbus High-Speed
Nicht weiterfahren
Expect the vehicle to run badly or not at all, with warning lights across the dashboard and possibly a car that will not start. Have it recovered rather than driven.
The useful thing to understand is what this code is not. It does not name a failed computer. The vehicle's computers talk to each other over a shared pair of wires, and this says the wiring itself — or something connected to it — has stopped that conversation working. So a page of fault codes from every module on the car is one fault, not a car that has failed comprehensively, and it usually costs far less to put right than that list suggests.
Things genuinely worth mentioning, because they are common causes and only you know about them: any recent electrical work, an aftermarket alarm, tracker, dashcam or parking sensors fitted, a jump start, an accident repair, or water getting into the car. Devices spliced into these two wires are a leading cause, and a workshop has no way of guessing one is there.
There is a simple resistance check across the two wires that tells an auto electrician a great deal in one measurement, so this is usually quicker to diagnose than it looks.
Was dieser Code bedeutet
A fault on the high speed communication bus itself, rather than with any module attached to it.
Every lost communication code in this corpus names a module and points, in the end, at one of a small number of shared things. This is a code for the most shared of them.
The bus is two wires. Twisted around each other and called CAN High and CAN Low, they carry every message the vehicle's computers send each other. The signal is not a voltage measured against earth — it is the difference between the two wires, and that single decision is why a network of thin wires survives in a vehicle full of ignition sparks, starter motors and alternators. Interference strikes both conductors almost equally, so it cancels out of the difference and the message arrives intact. Untwist them, or break one, and that protection is gone.
It is a party line rather than a set of private connections. Every module hears every message; each message carries an identifier saying what it is about rather than who it is for, and modules simply pick out what concerns them. When two want to speak at once the identifier decides who wins, and it is arranged so that a message about the brakes always beats a message about the radio. Priority is built into the numbering rather than managed by anything.
There is a free test for this, and it is worth knowing because it is unusually definitive for something that costs nothing. The bus has a terminating resistor at each end, typically 120 ohms, and they sit in parallel across the same two wires. So with the ignition off, measuring resistance across the pair should read about 60 ohms. Roughly 120 means one terminator or one end of the bus is missing. An open circuit means a broken wire. A very low reading means the two are shorted together. Four possible outcomes, each pointing somewhere different, from one measurement.
"Bus off" is a defined state and it is protective rather than broken. A module counting too many transmission errors removes itself from the network, so that a faulty talker cannot jam the conversation for everyone else. That mechanism is why a single failing module usually goes quiet alone — and understanding it explains the case at U0100 where one does not, and takes the whole network down with it.
The reading to take from a bus code rather than a module code: expect lost communication codes from everything at once. A dozen of them, stored across every module that can still store anything, is the signature of a fault here — one fault reported by everyone who noticed.
Wahrscheinliche Ursachen
Hier anfangen
- Datenbusleitungen beschädigt · mittel
- Korrodierter oder loser Stecker · einfach
- Ein anderes Steuergerät zieht den Bus auf Masse · Fachwerkstatt
- Schlechte Leitungsverbindung in einem nachträglichen Einbau · mittel
Seltener
- Wasser in den Stecker eingedrungen · mittel
- Busabschlusswiderstand defekt · Fachwerkstatt
- Gateway-Steuergerät defekt · Fachwerkstatt
Symptome
Beteiligte Bauteile
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