Electrical problem, B1644 code
 

Hey so I'm having an issue getting my LR turn signal to work. First I thought it was the bulb but after changing it I learned the problem was bigger than that.

I took the car into my mechanic and at first they thought it was the harness but after checking the codes and testing they concluded that it was my FCM(front control module). So I procured a FCM(used) and installed but the problem was still there. Most of the forums and manufacturers replacement instruction state that the FCM did not have to be reprogrammed for my car. Does anyone know if that is so? If its not then my problem is something else and my mechanics diagnostic was incorrect. I dont know what to do. I feel like I wasted money on a FCM but unsure cause it could be that it needs to be programmed. However if that was so I would think the replacement FCM wouldn't work at all if it was a programming problem.

Has anyone else experienced this problem with their magnum or dodge? If so please help. Hell I thinking of wiring the LR signal up to the LF signal so I have a functioning blinker.