Seat Leon electrical issues

I had something similar with my Leon, though I can't say for sure it's the same issue. Intermittent electrical problems are a pain. When you say 'failure of various systems,' can you be more specific? Does the 'service required' message come on with the 'check engine' light? Have you used a scan tool to pull any error codes? Knowing those codes would really help narrow it down.

Yep, that sounds familiar. By failure I mean the audio and navigation go haywire, sometimes the screen just blanks out. The 'service required' message sometimes pops up with the check engine light, other times it's just one or the other. No, I don't have a scan tool myself. What kind of error codes did you get?

Okay, the audio/nav thing, plus the random warnings, is ringing a bell. I got a bunch of errors related to CAN bus communication problems. The CAN bus is basically the car's central nervous system, letting all the different control modules talk to each other. If a connection is bad, modules can't communicate properly, which leads to all sorts of weirdness. Given your symptoms, especially the audio/nav issues, I'd suspect a bad connection to one of the control modules. Seeing as you don't have a scan tool I would recommend taking it to a workshop to check the control module.

Big thanks for your help! Took it to the workshop. Indeed, a defective cable connection to the BUS system was the culprit. Engine diagnostics confirmed the error. They sorted it out for 155€. Happy driving again!