Convertisseur CC-CC défectueux

The hybrid's replacement for an alternator: it steps a few hundred volts from the traction battery down to the fourteen volts that runs everything else on the car. When it fails, the twelve-volt system runs down exactly the way it would with a dead alternator — dimming lights, a battery warning, then a car that dies and will not restart — on a vehicle with no alternator to replace, which is where the diagnosis usually goes wrong first.

One measurement frames everything: with the system READY, the twelve-volt battery should sit around fourteen volts. Resting voltage instead means no charge is arriving — and then the question is whether the converter itself has failed or whether its enable and status wiring (the P0A08–P0A13 families) has stopped telling it to run, which is the cheaper and commoner answer. High-voltage territory throughout: qualified workshops only.