Außentemperatursensor defekt

The sensor measuring outside air temperature, drifted or failed. It does more than feed the dashboard display: the module uses it as the reference against which other temperature sensors are judged, and it informs air conditioning strategy, intake temperature correction and cold-start behaviour.

Position causes more faults here than failure does. These sit behind the grille or in a door mirror, and a sensor in radiator heat reads high whenever the car is stationary — which is why many vehicles freeze the displayed value below a certain speed and only update it once air is moving. A reading that is high in traffic and correct once moving is that behaviour, not a fault.

Its role as a reference is what makes a drifted one expensive to misdiagnose. A correlation code between two sensors names a disagreement without saying which is wrong, and if this is the one that drifted, the other sensor gets replaced for nothing. The cold soak settles it: after a night standing, every temperature sensor on the vehicle should read close to this one and to each other.

Mirror-mounted sensors fail from water ingress and from careless glass replacement, which is worth asking about where one has been changed.