Trial and error is the hard way to solve this. As I also have two Crossfires with very low mileage I have to watch out for bad gas clogging things up and causing misfires or worse. What needs to be done is to use a good scanner that not only reads error codes causing check engine light to go on, but include OBDII readiness monitors (smog check). I suspect there was a repeated failure related to the drive cycle tests. Buy yourself a decent scanner. I've lost count on how manner scanners I've aquired over the years for different reasons, and at different price levels. I've seen many other posts with forum members recommending their scanner of choice.

A quality low cost and easy to use scanner that provides a lot of good information is the BlueDriver available on Amazon. It's very conventient and easy to use through your smart phone.