Bad PCM?

[SuperB70]

Hi, I've been doing an LS1/4L60e swap to my customer '71 Buick Skylark convertible.
He had already bought an '02 Camaro engine, trans and it came with stock harness and pcm.

Well , We chanced the harness to painless kit and did everything as the install manual tells to do. Not so difficult thing to do. Car has an extra protection so had to install extra relay to controls feed to fuel pump but thats no brainer and has nothing to do with this.
I do know my way in car electric stuff..

So today I try'ed to get it running. Right after I turned battery on, it burned pcm/ diagnostic constant fuse. And I dont have keys turned on yet.

So at that stage there should not be any thing happening at the PCM, just standby current, after ignitionkey is turned then it should come to life.

My diagnose it that I have a bad PCM.

Anybody have any other ideas?