First I'd like to say hello.

My truck is starting to shift strange. As it warms up and I'm in drive, it will shift between drive and 2nd by itself. When I pull up to a stop lite, it's like it's stuck in drive and doesn't downshift. Ultimately it dies. I've checked my fluid and its fine. Any ideas? Oh and my engine light is on. Can a parts store find the code for the issue I'm having?

 

This sounds like your lock up torque convertor is staying locked and not releasing like it's supposed to at that time. I don't know if a parts store can read for that code. Your local Ford dealer can.