There's a Volvo TSB on this and Volvo will "sometimes" pay a dealership (up to) 3 hours to reset that, takes two trip cycles, BUT everytime we get one of those, we send out an hourly tech with the scan tool (Volvos VST) and it takes the guy over a day everytime. The car has to cool down between its two required trip cycles during this proceedure and in summer now, that will take a while. It's a major hassle for any dealer in states that are now testing/failing cars for that reason even though there's nothing really wrong with the cars emisions system.
A dealer needs to get the time to do that pre-approved by their rep and it's suppose to be a one time thing only. That means the next time, in 2 yrs if your car fails again for the same reason....you'll pay. It's become a bad scene, total BS IMO.