Skoda Fabia Diesel Battery Drain Issue

Sounds like an electrical issue. Have you checked the alternator is charging the battery while the engine's running? A multimeter across the battery terminals with the engine on should read about 14V. Any aftermarket electronics installed, like a dashcam or stereo? They can drain the battery even when the car is off.

Thanks for the quick reply. I'll check the voltage. I have a dashcam, but it's wired to switch off with the ignition. Could a faulty dashcam still cause such a heavy discharge, even when supposedly off?

The dashcam should be off, but they can draw power. However, given the error codes and the symptoms, a faulty battery sensor is a likely cause. They can cause issues with the charging system. With those symptoms and error codes, I'd get it checked by a workshop to save yourself the trouble.

The battery sensor was indeed the problem. The replacement cost 315€, but the Fabia is running perfectly again. Thanks for the guidance.