S80 Bypass Valve Error and Overheating

I had a similar problem with my 2012 Opel Insignia. The error message concerning a valve was misleading. In my case, it was a faulty vacuum system causing a cascade of errors. Is your Volvo's exhaust system functioning correctly? A blockage there can also lead to overheating.

By 'vacuum system,' do you mean the system controlling various engine components, like the EGR valve and turbocharger? I will investigate the exhaust system for blockages. Can a malfunctioning EGR valve trigger the bypass valve error?

Yes, that's correct. The vacuum system regulates several parts. An issue there could very well trigger seemingly unrelated errors. While I managed to diagnose the vacuum leak myself, it ultimately required specialized tools to repair. I would suggest getting it checked at a workshop.

It appears the bypass valve error was indeed a consequential error, related to a faulty sensor in the exhaust system. Repair costs were 0€. Thanks for pointing me in the right direction.