U0177: Kommunikationsverlust mit dem Sensor H des Rückhaltesystems
Was zu tun ist
The airbag warning light may be coming and going rather than staying on. That does not make it less serious — it makes it harder to find.
You can help more than any test here, and it costs nothing: notice when it happens.
- Does the light come on only after you have been driving a while, or only on the first cold start of the day?
- Does it clear itself on a different day, or after the car has stood?
- Does it appear on rough roads, or after one particular bump?
Write it down and give it to the garage. These sensors sit at the front of the car and go through enormous temperature swings — hot after a motorway run, cold overnight, thousands of times over. Connections work loose in a way that makes contact when cold and loses it when hot, or the other way round, and knowing which tells a technician where to look. If it happens over bumps rather than with temperature, that is a different answer again — a wire under tension, or a plug being held in by friction rather than by its clip.
Do not accept "we could not find anything wrong" as the end of it. The car stored that code because a check genuinely failed. A system that is unreliable now and then will be unreliable in a crash, and that is not a moment anyone gets to schedule.
Was dieser Code bedeutet
A restraints system sensor has stopped being heard from. See U0170 for the one-versus-several rule and U0478 for why an intermittent restraints fault is harder to find rather than less serious.
The intermittent open circuit is the version of this fault that gets dismissed, and the argument against dismissing it belongs here in its strongest form.
A vehicle presented with the airbag lamp out and a stored code is a vehicle that failed a check and then passed one. The stored code is the evidence. Nothing about a circuit that dropped out yesterday and is connected today makes it trustworthy — and a restraints system is only useful at a moment nobody can schedule.
So "we could not find anything wrong" is not a conclusion. It is a description of when the vehicle was tested.
What the owner can supply is the thing a workshop cannot: when. A crash sensor at the front of a vehicle lives through a temperature range nothing in the cabin experiences — heat-soaked well above ambient after a motorway run, down to whatever the night offers, thousands of times — and connections that have worked loose over years make contact when cold and lose it when hot, or the reverse.
Three questions, and any answer is worth more than a workshop test on a cold, stationary vehicle:
- Does it appear only after driving for a while, or only on the first cold start?
- Does it clear itself on a different day, or after the vehicle has stood?
- Does it appear on rough roads, or after one particular bump?
The last of those points somewhere different from the other two — a harness under tension, or a connector that is held together by friction rather than by its lock, both of which are found by moving the loom by hand rather than by measuring it.
Wahrscheinliche Ursachen
Hier anfangen
- Zeitweiliger Fehler in der Verkabelung · mittel
- Korrodierter oder loser Stecker · einfach
- Hitzeschaden an Sensor oder Leitung · mittel
- Wasser in den Stecker eingedrungen · mittel
Seltener
- Aufprallsensor bei der Karosseriereparatur verstellt · mittel
- Airbagsteuergerät defekt · Fachwerkstatt
Symptome
Beteiligte Bauteile
Information, keine Handlungsanweisung
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