nissan micra ecu/transponder anti-theft problem?

heater matrix blew soaking the ecu just below it-- changed the ecu for a second hand one from local scrapyard and the car will start but cuts out after approx 30 seconds so changed the temp sender thermister but car is just the same.. the key is chipped with a transponder on ignition barrel and wondered i that could be the fault yet when the transponder is disconnected the car stil does the same--any ideas