Hi everyone. I have a 2018 Octavia Mk3 facelift with factory auxiliary heating. When I try to start it using the remote, the LED blinks fast green, and when I try from the infotainment screen, it shows “auxiliary heating error.”

I scanned the car with a DS150E OBD tool and got the following error code: B138F4B – overtemp. If I clear the code and try again, it immediately comes back. In live data, the water temperature sensor reports valid values, but the outside temperature sensor shows “overtemp.” Although in a different data list it shows the correct outside temperature (around 8°C).

My first thought was a bad sensor, but since I can still see the correct temperature reading somewhere else, I’m not sure. Does anyone know what might be causing this or which sensor could be faulty?

For anyone with the same issue.
I just fixed mine. I replaced the temperature sensor on the Webasto (Skoda part number 5Q0 898 047, Webasto article number W9045211A). It’s really not that hard to do at home, although there are a few more difficult or tricky parts. One example is the crimped fuel line on the Webasto - at least for me, the main issue was that I didn’t have a suitable crimp on hand. Reinstalling the wheel liner also took quite some time.

The original thread about this issue:
https://www.briskoda.net/forums/topic/527570-aux-heater-false-overheating-fault/