2012 Caprice Motor swap ECU issues

[J0nesy]

Recently bought HPTuners for my own project, but had to use it for the first time helping my brother with his engine swap.

Car A is a 2012 Caprice that he wrecked. Motor already had DOD delete, Cam, CAI, and a tune from a guy in Louisville, KY.
Car B is a 2012 Caprice roller that he bought recently.

Pulled motor and tranny from Car A and dropped it into Car B, adding some Kooks headers in the process. I was able to pull the tune, and turn off VATS. Car still had a P0513 Engine Immobilized code that I couldn't get to clear. We started the car multiple times while we traced down a couple loose hoses and connections. He was able to drive it home (15 miles) the next day. The following day he went to move it and it won't even turn over. Pulled the code and it is a U0100 Lost Communication with ECM/PCM. When I hook up to it with HPTuners it doesn't see the ECU at all, only the TCM.

We have checked all the ground connections that we can find, and cleaned them. Have unplugged and reseated the ECU connections. Have left the battery disconnected for 60+ minutes at a time. The fuses all test good in the underhood fuse box.

What else is there that we should check? Or did the security system somehow lock us out of the ECU?

[5FDP]

Which computer did you use?

[J0nesy]

Computer is from Car A, the wrecked Caprice. The roller did not come with a computer. The body control module is still the original Car B module. I think our next step is to swap the bcm's, that way all the vin numbers should match between all the computers. Although if I understand correctly, disabling VATS should make this a non issue?

[5FDP]

Do you know if you did a write entire with the VATS?

[J0nesy]

I did do a write entire. Otherwise the OS changes (vats) wouldn't have taken effect and let us fire up the car.

[veee8]

It shouldn't keep you from communicating. There is a wiring problem somewhere. Check under the car, trans harness etc. Make sure nothing got pinched or burned on the headers. You will lose ECM communication if the TCM doesn't complete the data lines loop.
You did the correct procedure for this situation by disabling VATS/starter checks and obviously worked since you were able to drive it..

[J0nesy]

It shouldn't keep you from communicating. There is a wiring problem somewhere. Check under the car, trans harness etc. Make sure nothing got pinched or burned on the headers. You will lose ECM communication if the TCM doesn't complete the data lines loop.
You did the correct procedure for this situation by disabling VATS/starter checks and obviously worked since you were able to drive it..

Thanks for the info. This is the answer I was hoping for. Now we just have to trace down the wiring and figure out where we are losing power to the ECU at.

[rcodea1]

How did this turn out? I too am getting a U0100, but not turning over and I can read/write to both PCM and TCM.

~Ryan
Charleston, SC