Rear Diff Won't Lock

Here's a possible candidate.
https://www.ebay.com/itm/275757365668?

 

UPDATE:

After a lot of help from Dm93 between diagnosing the problem and sourcing the correct part. I've got the rear diff to lock. It took some driving around for it to engage but now it engages freely. It's kind of impressive after not being used for the 9 years that I've owned it. But I guess that's just typical toyota reliability.

One thing that I still can't wrap my head around is why the previous owner decided to swap the 4wd ecu. When I bought it in 2016 it was 4 years old with 76k miles. It seems unlikely that an ecu would fail at such a premature age. But I guess I'll never know the answer to that.

Thanks again for the support guys!!!

 

Alot of them get swapped unnecessarily chasing 4wd issues because most people don't understand how the system works, they just swap parts until something sticks.
That was one of the reasons behind me reverse engineering the system and building the 4wd help thread so we would have a way to effectively diagnose the system and only replace the actual bad part(s).

In any case glad you got it going