U0055: Bus de communication du véhicule D
Que faire
If your battery keeps going flat when the car is left for a few days — while starting perfectly when you drive it daily — read this page. It is very likely the explanation.
A parked car is not switched off. It is asleep, drawing a tiny current to keep its memories and watch for the key. And going to sleep is something all the computers have to agree on — any one of them can keep the whole network awake.
When one does, the car never fully settles, and the battery drains over a few days. That gets answered with a new battery, then an alternator, then another battery — because nothing is wrong with any of them.
There is one measurement that settles it, and one way of getting it wrong that causes most of the arguments.
A car does not go to sleep the moment you lock it. Timers run — some computers stay awake for minutes, a few for the best part of an hour — and the current falls in steps as each one gives up. A reading taken five minutes after locking always looks alarming and means nothing.
So ask for the drain to be measured after the car has properly settled, with the fall watched rather than assumed. A current that never drops, or that drops and then climbs again on its own, is this fault — and from there it is a matter of unplugging computers one at a time until the car finally sleeps.
Ce que signifie ce code
A fault has been detected on vehicle communication bus D. See U0028 for why the letter must be resolved first and U0003 for the electrical faults.
This page carries the argument that explains the commonest expensive misdiagnosis in the whole range: a bus that will not sleep.
A parked vehicle's networks are not switched off. They are asleep. Modules drop into a low-power state, the bus goes quiet, and the vehicle settles to a draw measured in tens of milliamps — enough to hold memories and watch for a key, and little enough to leave a healthy battery usable after weeks.
Going to sleep is negotiated rather than commanded. Every module has to agree, and any one of them can hold the network awake — legitimately, while it finishes something, or wrongly, because a fault means it never finishes.
So there is a whole class of bus fault that only exists when the vehicle should be doing nothing, and it does not present as a network problem at all. It presents as a flat battery. The vehicle starts perfectly when driven daily and is dead after a weekend, and it gets answered with a battery, then an alternator, then a second battery.
The measurement that settles it is the parasitic draw, and there is one way to get it wrong that accounts for most of the disagreements about it.
A vehicle does not sleep the moment it is locked. Timers run — some modules stay awake for minutes, a few for the better part of an hour — and the draw falls in steps as each gives up. A reading taken five minutes after locking is meaningless and always looks alarming. The measurement has to be taken after the vehicle has settled, and the settling has to be watched rather than assumed.
A draw that never falls, or falls and then rises again on its own, is this fault — and from there the method is U0040's: disconnect modules one at a time and watch which one lets the vehicle sleep.
Causes probables
Commencez ici
- Un autre calculateur maintient le bus à l'état bas · spécialisée
- Épissure de câblage médiocre dans une installation non d'origine · modérée
- Câblage du bus de données endommagé · modérée
- Connecteur corrodé ou mal enclenché · facile
Moins fréquent
- Calculateur passerelle défectueux · spécialisée
- Infiltration d'eau dans le connecteur · modérée
Symptômes
Composants concernés
Des informations, pas des instructions
CarGeek est un ouvrage de référence, pas un manuel d'atelier. Ses pages sont rédigées à partir de sources publiques et de ce que d'autres ont constaté, jamais à partir de la documentation technique du constructeur ; elles peuvent donc être erronées ou incomplètes pour votre véhicule précis. Une partie de ce qu'elles décrivent présente un risque réel : haute tension, carburant sous pression, énergie accumulée, pièces chaudes ou en mouvement.
Avant d'agir sur quoi que ce soit, faites-le vérifier par une personne formée, en suivant la procédure du constructeur pour votre véhicule. Rien ici ne remplace cette procédure.
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