U0301: Incompatibilité logicielle avec le calculateur moteur
Que faire
Nothing is broken. Two of your car's computers are each working perfectly and running software that was never meant to work together.
That is worth understanding before any money is spent, because there is no part that fixes this — it is a programming job, not a repair.
The most important thing to know: do not let the engine computer be replaced on the strength of this code. It is one of the most expensive parts on the car, it has to be programmed to the vehicle, and it may well be the half that is already correct — the code names two computers that disagree, not one that is broken. A replacement arrives with whatever software the supplier put on it, which is often neither of the versions already in your car, so it can leave you with a second mismatch and a large bill.
Say what has been done to the car recently. A module replaced — especially second-hand — a software update or recall, an interrupted reprogramming, or something retrofitted. One of those is almost always the cause, and knowing which saves the whole diagnosis.
Expect this to need a dealer or a specialist with access to the manufacturer's calibration data. A general garage with a code reader may not be able to resolve it however capable they are, and that is worth establishing before paying for diagnosis rather than after.
Ce que signifie ce code
A module is running software that does not belong with the engine control module's. U0300 establishes the family and should be read first; this page adds what changes once a code names the partner rather than reporting a module's own inconsistency.
That is the whole difference and it is worth stating plainly. U0300 says a module has found its own software inconsistent. This code says two specific modules have compared notes and disagree — and it names one of them.
Which produces the trap this page exists to prevent: the named module is not the accused.
A mismatch has two halves and either can be the wrong one. The reporting module may be newly programmed and correct, objecting to an engine module still on an old calibration. Or the engine module may be current and the reporting module left behind. The code cannot tell you which, because from inside the vehicle there is no such thing as the wrong one — only a pair that does not agree.
So "replace the engine control module" is wrong twice over. It is wrong because this is software rather than hardware, and wrong again because the engine module may be the half that is already correct. A replacement arrives carrying whatever calibration the supplier shipped, which may be neither of the two versions already in the vehicle — so the usual outcome of replacing a module here is a second, different mismatch on top of an expensive part.
The right question is not "which module is faulty" but "what is the current released calibration set for this vehicle identification number", and then bringing every module on the affected network to it. That is a dealer or specialist question, and it is answerable in minutes by somebody with access to the manufacturer's data.
Why this particular code appears more than most: the engine module publishes the values everything else consumes — engine speed, load, torque, coolant temperature, throttle position, fuel status. The more partners a module has, the more of them notice when its dialect changes. So breadth here reflects the engine module's role rather than the seriousness of the mismatch, and a long list of complaining modules is not evidence that the engine is in trouble.
Causes probables
Commencez ici
- Logiciel mis à jour sur un seul calculateur · spécialisée
- Calculateur d'occasion verrouillé sur un autre véhicule · spécialisée
- Configuration du calculateur erronée après remplacement · spécialisée
- Programmation du calculateur interrompue · spécialisée
Moins fréquent
- Moteur reprogrammé ou logiciel non d'origine installé · spécialisée
- Calibrage logiciel obsolète · spécialisée
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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Rien n'a encore été publié à ce sujet. Tout ce que vous avez trouvé mérite d'être noté — même une impasse épargne à quelqu'un le même après-midi.
Ce qui rend un compte rendu utile :
- La voiture — marque, modèle, année et moteur. La même panne ne se comporte pas pareil sur chacune.
- Ce que vous avez mesuré, pas seulement ce que vous avez remplacé.
- Ce qui a réellement résolu le problème — ou que rien ne l’a résolu, ce qui est utile aussi.
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