Check Engine and Cruise Control Lights

[wdussasult]

I have a 2015 Legacy (2.5). I commute to work on Interstates about 450 miles a week. Last Friday those two lights came on. The manual said that the Check Engine light would come on if the Gas cap wasn't tightened. I took it off and retighted it and the lights went off after several starts the next day. On the way home last night, the lights came back on again. I retighted the gas cap, but I feel like something may really be wrong. The manual says not to drive at high speeds with these lights on. But that is really not an option for me with my commute.