Seat Toledo MOST bus fault

That sounds nasty! A MOST bus fault is basically the data transmission network in your car, using fiber optics. No audio, no navigation... sounds like a component on that bus is kaput. Did the error message give you any clues about which unit might be causing the problem? What kind of car diagnostics did you run? Is it a continuous error or intermittent?

The error code didn't point to a specific unit. When you say 'component', are we talking about the head unit itself, or could it be something else entirely? Also, when you say fiber optics, does that mean I can't just check the wiring myself?

Component could be any module connected to that MOST bus system - the radio, amplifier, navigation unit, even some safety features depending on the car. And fiber optics means light signals, not electrical signals through copper wires. So you can't just visually check the wiring, you'd need special equipment to test the fiber optic connections, plus the car diagnostics software to really dig in. Honestly, with that kind of issue, I'd recommend taking it to a workshop with experience in car diagnostics and MOST bus systems. Could save you a lot of time and potential further damage.

The shop confirmed a MOST bus issue and pinpointed a faulty control unit after diagnosis. It cost me around 1000€ as predicted, but everything is working now. Thanks for your help and advice!