No start after ECM was replaced

Just so I am understanding the progression on this, you had an issue with the vehicle, replaced the ECM and it ran poorly with the new ECM but ran fine with the old ECM.

Then you swapped the ECM with another vehicles ECM, and you can start the vehicle because you are not able to get it started due to the keys not being programmed?

If that is the case, then I suspect that is because you cannot swap ECMs from other vehicles.

I would suggest starting with scanning for codes on this ECM and you should have P1576 which is telling you that the ECM is not registered.

Here is a guide that will talk about this:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Basically, anytime you put a new ECM in the vehicle, you need to register the immobilizer system in it.

Please let us know if there are codes in the ECM as the vehicle sits and we can go from there. Otherwise, we need to put the original ECM in the vehicle and confirm it is in running order still.

Then the replacement ECM is most likely faulty so I would replace it again and not use one out of another vehicle.

Please correct any of this if it is not correct.

Thanks