I need help with my car

That's VERY unlikely, Ed! The most common occurrence of a CEL in that era Subies is a PO420 for cat conv operation out of calibration due to richer winter fuels. But there are MANY other causes. Just scan and read the code(s), record them, clear them, and report back if they recur. Don't worry about the tranny unless there's a missing post here re loss of ATF or rapidly blinking AT light.

My Subaru is a 2010 and is doing the same thing. Throws a code for transmission but it runs fine this has been happening for a year and a half. I just wish I knew what it is and what it's going to cost

Dunno. Apt more to be a sticking valve solenoid rather than overheating. What's the code?