Hey, everyone, I'm having issues with a 2006 Mazda 3 2.3L. The AT light and check engine light is on and the car is stuck in 3rd gear with a really rough gear change into reverse. I've replaced the TCM with one from a junkyard and believing it was faulty I bought a brand new one and still the same issue. I've checked all the fuses and everything seems to be working properly except the car not being able to communicate with the TCM. Any help would be appreciated

 

The TCM needs to be programmed to the vehicle, using the data from the old tcm or as- built data from Mazda. What DTCs where you getting before?

 

I've heard both that it doesn't need to be programmed but also that it has to be programmed. I've tried taking it to the dealership to program and they said they could not program it.