all4pirelli

Hi I've got a 199 F150 6cyl. My scan tool does is not able to connect to the computer does anyone know why this may be. I have never had a problem scanning any other vehicle. Im not using a cheap scanner either so lets not start there. One thing ive noticed is that with other vehicles when i turn the scan tool on the backligt comes on. With my ford it does not. If anyone knows about a problem with ford connections please advise..
J....

I got it figured out there was a broken wire in plug 16 which is power 12v+..Thanks for looking..