This has been an issue for some years, beginning with the advent of the highly computerized S80. It seems that Volvo have finally heard the many, *many* complaints and decided to do something. Acting on this kind of problem may be one of the better things to come from association with an American manufacturer - one accustomed to being sued for anything and everything . . .
The basis for this is a "fault" seen by the OBD computer system when the gas cap is less than fully closed. The absolute pressure in the gas tank does not respond to computer commands and this is seen as a failure of a portion of system integrity relating to control of emissions from the tank and/or the filtering system through which the tank breathes.
Most owners don't like unending fault messages and don't have the needed goodies to reset them, so visit their dealer for help. During warranty, the dealer was pretty well stuck with having to take the time to pacify his customer *and* faced the inevitable word from Volvo that they would no longer honor the same request from a VIN associated with an owner who seemed unable to set the cap properly. Didn't go over too well!
I just received the letter relative to our S60AWD. Maybe in for the fix later this week.
bob noble Reno, NV, USA