Hi , I bought a 2004 express 2500 5.7l cng with 39k on it. Ran perfect for 6 months. I started it one day, warmed it up for about a minute, started to drive it , and it went into limp mode. Got it back home, about 2 blocks. Tried to diagnose with scanner, but no power at obd port. I only see 4 wires at the back of one port. Has anyone had this problem? I need a cng wiring diagram/schematic, and some cng knowledge. The van came from Michigan, so lots of rust. Thanks for any help

 

dlc connector is powered by the cig fuse....check for a blown fuse.

 

I did check the fuses, I will check again.
does anyone have a obd port wiring schematic? I'm trying to determine if previous owner took any wiring out to run backup camera or, who knows? Thank you for your response

 

you can find schematics here:
https://charm.li/