why does my durango die when i replaced ecm

sounds to me like the ecm you put in it has security enabled on it and needs to have the keys programmed into it. Try and start the car and check to see if the security light comes on and stays on. if the security module is not happy it will stop the engine after a couple of seconds. hope this helps

one other thing is you might have to get the pinion factor reprogrammed in your abs because you switched the ecm. I know on 2003 and under as soon as you plug in a new ecu it wipes the abs programming and continues to ding nonstop when the engine is running.

Does it have the chip in the key

If it's got the chip in key you triggered the anti theft on it you'll have to bypass the anti theft security system on it or take it to the dealership and have it reprogrammed

You need to plate the VIN number to the ECM most shops or lock master can do it lock master is cheaper