Engine Swap VATS question

[Dsiigh]

Hello All,

Hopefully this post is in the right place, and I apologize in advance if its a little... verbose lol. So im in the middle of a engine swap in my 2013 Cadillac ATS, I'm using a factory V3 Harness, Silverado 8l w/ matching t87a and 2017 E92(A?).
So far the swap has been pretty plug and play, notable differences just for context is X50A (fuse box) is the same connector but some circuits are just swapped around but they are all there. Also the 2.0 this chassis came with uses a black box FPCM (think gen 4) basically just PSI x RPM, and the Gen 4 stuff uses the silver slave module that just does what the ecm commands, from what I understand. But the LF3 uses the black box and also has an E92 so i figure it can communicate at a minimum.

Now on to the problem: I have a no crank condition, basically the ECM isnt sending voltage to the coil of the starter relay. I thought it was related to VATS because i was originally using a used pcm where the PIN and VIN didnt match, but I have since bought a brand new ecm from GM. Plugging it into the car let it take on my PIN and putting a file on it with SPS put a vin on it. - not MY vin to be clear, for tune vin mismatch reasons, but SPS did did me do a antitheft learn successfully, which wasnt possible with the used ecm, so that all looks promising to me. According to SPS the BCM IS sending "start request" over GMLAN, but the ECM still wont activate the coil. I have communication everywhere else... TCM is reporting gear to the cluster, Fuel level is also being reported to the cluster so im pretty confident that GMLAN isnt the problem.

So my question(s):
Is there anything else that needs to happen to satisfy the ECM to close Cir 625? ie any other modules it wants to see to not just shut down?

The ECM currently has a file from a 17 silverado 6L80 in it, just because i already had a license from the used ecm and figured it shouldnt make a difference, but now im thinking that the 6L tune isnt happy about seeing a T87? anyone ever heard of something like that? or maybe i should try a file from an actual car? (v3, zl1)

Hopefully someone could offer some advice.

Thanks in advance

[Dsiigh]

Okay so minor update:

Hooked up a different scanner and as far as I can tell the ECM sees everything it needs and at least thinks its activating the relay. Crank request: Yes, Starter Relay Command: On, Park/Neutral: Yes. But I'm still not seeing any voltage on p63 on X1 (cir 625). Something I did see that is promising is under IMMO info it does say that "Immobilizer security code accepted" is No, and also that it is immobilized. Weird because SPS (techline, whatever) completed the IMMO learn successfully. So now the question is: VATS only disables fuel/spark, correct? Id just think its weird if the ECM was inhibiting the starter relay while also reporting that its activating the starter relay.

I also forgot to mention in my last post that the relay is hot, and I can manually crank jumping 87 and 30 on the relay, there is continuity between p63 X1 and 86 on the relay, and between 85 and chassis ground.

I have a VATS off file from the repo, but i just wasn't sure if i wanted to license this VIN yet in case i have to do something different with the ECM, but ill load that up tomorrow and see what happens.

20230818_174052000_iOS.jpg20230818_153939051_iOS.jpg

[Dsiigh]

Quick update: I ended up getting it… I changed the VIN in the BCM to the ECMs vin did the anti theft relearn, and changed it back to my original VIN and that worked for getting the start request to work. I also ended up having to run an external relay as the fuse box pin for the relay was damaged and it seemed like the better choice just to be sure.

Now just need to get it buttoned up and tuned.

Also, I was able to convert and Escalade cluster to V with the same VIN change method. I still need to modify the lens/bezel but I’m pretty happy with how it’s going so far.

https://youtube.com/shorts/UCjxgBjSo...ChGSJkkYHFSkJd

[chadtunes]

Quick update: I ended up getting it? I changed the VIN in the BCM to the ECMs vin did the anti theft relearn, and changed it back to my original VIN and that worked for getting the start request to work. I also ended up having to run an external relay as the fuse box pin for the relay was damaged and it seemed like the better choice just to be sure.

Now just need to get it buttoned up and tuned.

Also, I was able to convert and Escalade cluster to V with the same VIN change method. I still need to modify the lens/bezel but I?m pretty happy with how it?s going so far.

https://youtube.com/shorts/UCjxgBjSo...ChGSJkkYHFSkJd

Thats cool, I want to pick your brain about that more.

Can I plug in ECU from another engine to my existing harness and pull the config and vin without messing anything up?