what would cause no pcm ground signal to ac relay in battery junction box

hi i am hoping i can get some help and do appreciate all and any help. i just put a motor in a 2005 ford taurus 3.0 ohv it went smoothly and had no problems runs great and cooling fans operate it was a used very complete engine swap 15,000 miles on used motor this motor did come with complete engine harness i have studied my schematics and cant come up with an answer ac low side switch has power across red and purple wires to ac over presssure switch which turns into a green with white tracer wire that goes to pcm i have ohmed out this wire in harness to pcm no problem also i went to ac relay missing ground from pcm to trigger relay it is a pink wire which i also ohmed out in harness if this wire is grouned ac will engage this is a manual ac system i was dumb enough to install my scanner to check bcm codes but there was no options cause its manaul ac i guess