CEL light on! First time.

[shaman1204]

Got my first check engine light this past Saturday. On the way to the Cubs game I had the top down and it was super hot sitting in stop and go traffic so I put the top up and turned the a/c on. About 30 seconds later I got the CEL. Went to Pep Boys and they wanted $84 to run the diagnostics, but did a search here and I guess I can take it to Autozone for free. My question is, I think I am having a problem with my tiptronic transmission. To best describe it, when slowing to a stop the car shifts down to 2nd but it seems like it slips when coming to a complete stop and lurches forward when engaging 2nd. Would a transmission problem cause a CEL? For what its worth the engine has been running like a top. Sorry for the long post.