Volvo S80 sporadic errors

That sounds frustrating. Does it seem to happen more often in certain conditions, like when it's hot or cold, or after driving for a while? Also, what kind of errors are stored in the memory? Knowing the codes would help narrow things down.

Good point. I haven't noticed a specific pattern regarding temperature. As for the error codes, could a faulty cable connection to the BUS system cause these symptoms?

Yes, a bad BUS connection could definitely explain the random system failures and stored errors. Since it’s sporadic, I’d say a workshop visit is in order to check all the relevant cable connections. It's probably something simple, but chasing it yourself could take ages.

Thanks for the insight! I took it to a trusted shop, and they found a defective cable connection to the control unit, just as you suspected. Repair cost was 155€. Problem solved!