Skoda Fabia Diesel Overvoltage Errors

Sounds like a headache. I had something similar happen with my old Peugeot 307. A flood of seemingly unrelated errors popping up, systems going haywire… turned out to be the voltage regulator. Have you checked that? A faulty regulator can easily cause overvoltage, which then fries sensitive car electronics. Also, since you mention a weak battery, it could be dragging everything down and causing weird readings. Circuit protection should kick in, but sometimes it's not perfect.

Voltage regulator is a good point. How did you diagnose the regulator on your Peugeot? Was it throwing specific codes, or was it more of a process of elimination? And how did a weak battery give you a high voltage error?

On the Peugeot, it was a bit of both. There were some voltage-related codes, but nothing definitive screamed 'regulator'. We used a multimeter to check the voltage output at the battery with the engine running. It was consistently higher than it should have been, confirming the overvoltage situation. Regarding the weak battery causing a 'high' voltage error: a significantly discharged battery can create a larger voltage differential when the alternator tries to charge it, potentially leading to temporary voltage spikes that trigger the overvoltage detection. Given the symptoms and the age of the car, I'd suggest getting the battery professionally tested and the charging system checked at a workshop. It’s better to be safe than sorry when dealing with car electronics.

It was the battery. Heavily discharged and defective, according to the workshop. A new battery fixed it and all those fault codes disappeared. Cost 290€, but at least the Fabia is running smoothly again. Thanks for your help.