2000 Honda Accord EX 6 Cyl 3.0L
P1607 Error code on every ECU my mechanic has put in so far. It's been in limp mode every time.

I have been having this same diagnostic code throw even though I have replaced the ECU twice. The ECUs are from scrap parts so there is a vague possibility that they all have the same issue with them -- but it just feels very unlikely at this point.

At this point, I'd like to manually check the wires and ground to see if there is an issue. My main question would be the locations and what to look for... I'm having to DIY this for now.
I want to check the ground grounding the ECU along with the wiring harness for the ECU to see if I can tell that there's an issue. I'm sorry for my naivety and ignorance, but what diagrams are out there that allow me to tell what I'm looking for? This is my only car and it's already been out for over a month while I was replacing the ECUs. I'm taking care of my dad and really need to get him to doctor appointments. I know how to look at and decipher diagrams if I just get a good starting point if you could please help me.

I would love some help with this. I've spent so much money trying to fix it already, and my mechanic is scratching his head right now. We are in a rural area so there's not a lot of options.