2002 Chrysler Town and Country ECM Questions

Hello,

We recently got engine code P0601, which all research seemed to indicate meant we needed a new ECM.
To avoid the damage a dealer could do price-wise, I found a business that restores ECMs.
I unplugged the battery, replaced the ecm, and about an hour later, the light came back on. Per the businesses' directions, I unplugged the battery and let it sit for 24 hours. They said I shouldn't have unplugged the battery in the first place.
So they sent me another one. This time, the engine light came on in less than 5 minutes.
What else could the problem be? I didn't see any fuse that would seem to be related to the ECM.
Other explanations on the code referred to a shorted input sensor or electrical circuit. How likely is it to be one of those, and how would I fix that?
Any ideas what's going on with our vehicle?
Thanks in advance for any ideas you have!

Eliott