U0299: Perda de comunicação com o módulo B de controle do conversor CC/CC
O que fazer
The car should keep working — you have two of these converters and one is still doing the job — but get it fixed promptly rather than leaving it.
These converters are what keep your 12-volt battery charged; your car has no alternator, so they are the only thing doing it. Right now the second one is covering for the first, which means the safety margin has been used up. If the remaining one fails too, the car will stop working entirely once the 12-volt battery runs down — see U0298 for what that looks like.
Watch for signs the remaining converter is not coping, and treat any of these as a reason to go straight to a workshop rather than waiting for an appointment:
- Lights dimming, or warning messages about electrical load
- Heating, seat heaters or other comforts switching themselves off for no reason
- Any warning about the 12-volt or auxiliary battery
Comforts switching off on their own is the car rationing power, not several things failing — but it does mean the remaining converter is struggling.
Do not investigate this yourself; it sits on the high-voltage side and those voltages are lethal.
O que este código significa
The second DC to DC converter control module has stopped being heard from. See U0298, which explains why this converter is the alternator's replacement and why losing it strands a vehicle.
A second converter exists for redundancy or for capacity, and which of those applies to a given vehicle decides how serious this is.
Where it is redundancy — a deliberate second unit so that losing one does not immobilise the vehicle — the remaining converter carries the 12-volt system and the vehicle continues to work. That is why this code is marked drivable while U0298 is not. It is still a fault to fix promptly, because the redundancy that is protecting you right now has been used up: a second failure would produce the full U0298 situation with nothing left in reserve.
Where it is capacity — two converters sharing a larger 12-volt load on a vehicle with substantial equipment — the remaining unit may not manage everything. The vehicle will typically shed load, switching off comfort and convenience systems to protect the essentials, so an unexplained loss of heating, seat heaters or other accessories alongside this code is the vehicle rationing rather than several things failing.
The distinguishing evidence is the 12-volt battery's behaviour. Holding up normally means the remaining converter is coping. Dropping while driving means it is not, and that puts the vehicle on the same countdown described at U0298 — in which case treat it with the same urgency.
So the advice is: get it fixed promptly rather than urgently, but watch for anything suggesting the 12-volt system is losing ground — dimming lights, warning messages about electrical load, systems switching themselves off. Any of those changes this from a booked repair to a get-it-there-now.
The high-voltage caution at U0298 applies unchanged.
Causas prováveis
Comece aqui
- Alimentação ou massa do módulo inoperante · moderado
- Conector corroído ou frouxo · fácil
- Fiação do barramento de dados danificada · moderado
- Conversor CC-CC com defeito · especializado
Menos comum
Sintomas
Componentes envolvidos
Informação, não instrução
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Experiência da comunidade
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