I'm new to this forum, but here is my "take" on Check Engine alerts in general. Obviously, they "mean" something, but the question is what do they mean, and do you need to care (i.e. spend money to fix whatever it is). Technically speaking, "modern" cars have on board electronic/computer modules that measure and monitor and control almost everything. If a Check Engine warning led comes on it indicates that, at least at some moment in time, one of the monitors detected that something was out of spec.
So. What do ya do? Well, a few years ago the diagnostic monitors usually were set up in such a way that the owner could find out how to read the code(s). Some had some way to be read by using a jumper wire. Some flashed a series of SOS like patterns. Some required that you hold down a button while you turned your ignition key. More recently, there has been a move to OBDII technology. This technology requires the use of a Code Reader. Around here we have a chain of auto parts stores called AutoZone that will "read" Check Engine alert codes for free. Maybe you have such a place in your parts.
Once you have the code and what the code means, then it's decision time. The alert could be a one time thing or could indicate a major underlying problem. The conservative approach is to fix whatever the code says is broken. Unfortunately, though this sounds like the wisest route, sometimes the Check Engine code thrown is inaccurate or misleading. So the more maverick (cynical?) approach is to find somebody else who has more knowledge about cars in general and, hopefully, Volvos specifically to pick their brain.
I myself am riding right now with two recently thrown Check Engine codes: P0243 - Turbocontrol sporadic and P0302 - Cylinder 2 misfire. I have both "problems" on watch to see whether they recur or maybe even lead to other codes. Meanwhile, everything seems to be running fine and performance is not in question.
What code are you getting? Once you know, you can go from there...