Logiciel mis à jour sur un seul calculateur

Two modules that used to agree no longer do, because one of them was reprogrammed and the other was not.

Modules do not simply exchange numbers; they exchange numbers in a format both ends have to understand, and manufacturers change those formats between software versions — a value gains a bit of resolution, a message is split in two, a field means something slightly different. A module updated to a newer version speaks the newer dialect to a partner still expecting the old one, and the receiver rejects what it gets as impossible rather than misreading it.

That is why this shows up as invalid data rather than as lost communication. Everything is arriving, on time and correctly formed. Only the content is unacceptable.

The diagnostic signature is timing, and it is decisive: this appears immediately after work rather than out of nowhere. A dealer visit, a recall action, a module replaced, an over-the-air update, a retrofit. A fault that started the day the car came back from somewhere is this until shown otherwise, and the question worth asking is not what broke but what changed.

The fix is a software level, not a part. Bringing every module on the affected network to the manufacturer's current released set is the repair, and replacing hardware in the meantime achieves nothing — a new module arrives with whatever version the supplier shipped, which may be neither of the two already fitted.

One practical warning. Reprogramming needs stable voltage for the whole session, and a battery that sags part-way through leaves a module worse off than before — see the calibration integrity argument at U0441.