I have a 2001 Civic DX with 55k miles. A two days ago I notice a slight slip when automatic transmission shifts from 2nd to 3rd gear. The next day I take to my mechanic. He drives it and says he can't find anything wrong but tells me that the transmission fluid is due to be changed. He changes transmission fluid and I'm on my way home from the shop (approx. 20 minutes after I leave his shop) There's stop and go traffic and then traffic picks up. I give it gas and it down shifts and then the engine light comes on and the transmission just stops working. I come to a complete stop and it doesn't matter what gear I have it in, my car doesn't even move an inch. Can anyone tell me what happened?