Just got the car they changed the motor and said the ecu needed changed how do I test it

 

Brittob80, that is going to require getting a computer that has a program on it called SDD. It is a program that is mainly meant for jaguar dealerships, but there are copies out there that the general public has gotten their hands on. Through that program, you can access the computer through the port under the steering wheel. That will tell you any issues with the comm busses of the car, the PATS system (which may be wonky now after the motor change), and any other systems in the car.

Granted, if you put the key in with a fully charged battery, look at the center console as you rotate the key to the START position. Does a red light light up? If yes, then you have a security issue and you have an issue with the ECM not getting the information from the keyfob allowing starting of the car. If there is no red light, then your problem most likely lies in a bad starter (not a common issue) or a bad battery cable (most likely).