replaced ecm in my 2014 nissan maxima sv after hitting a deer. Now my car will crank, but won't start.

 

Does reprogramming of keys to new ECM, or new ECM to existing keys need to be done?

 

I have never done this, but alldata says you have to program the ecm to the vin

 

I took my car to nissan dealership. They told me after putting new ecm on my car, it would crank but not start.

 

This might be a bit late, but yes any new or used ecm needs to be programmed otherwise the vehicle will not start.

Now if the vehicle does not run after properly programming the ecm, then the dealership should know what is causing the stall.