I have a 2006 S60 2.5t and have had a few error messages pop up since I bought it used, but they've never affected performance. These recurring messages are "Brake failure, stop safely", "Engine system service required", "Anti-skid service off", as well as the Miles until empty showing as "9999". Other random and very uncommon things have been all gauges dropping to zero, the sunroof not working for about an hour long period, as well as CELs U0002 for High speed canbus network error and one for a wheel speed sensor... both of which reset on their own and have not popped up again. The brakes have never failed, traction control doesn't turn off. All this to ask if anyone has experienced similar things and traced it back to a specific module or issue, maybe the ECM? It went from being my daily to my project car now and I'm not in a rush to throw money at it, just want to get any leads I can for the future because I really do like the car and want to fix whatever the previous 5 owners did to it.
(I don't have VIDA but it's likely the next thing I'll buy for the car)

 

A good first step would be to scan the car with a compatible scanner. VIDA would be the best choice for that.

Abs warning means there's a code - could be a false code because the abs control unit is known to fail.

Instrument clusters are problematic also, bad connections cause problems. Some DIYers have fixed theirs but a company such as xemodex can fix for the DIM and ABS control units if needed.

Sunroof could be related to the alarm siren module back up battery leaking - does your alarm work normally? (lock car with window down and pretend to break in by opening the door from the inside when locked)

Some cars have problems with water intrusion into the CEM - I don't think a 06 s60 is high on that list though.

 

Really appreciate all this. Yeah my alarm works fine, tested it a while ago when that issue came up. I'll have to check for leaking and get VIDA, but again appreciate all this and I haven't heard of Xemodex so I'll check it out if needed.