I have a 2001 GMC sierra with the check engine light on, but to try and hookup a scan tool I get no power from the port. Someone told me it could be a fuse does anyone have a full wiring schematic that includes the ciegertte lighter cirucit????

 

Did you check the cigar fuse in the electrical center junction box in the engine compartment? When this fuse blows, you won't have power to the DLC. Usually that's what the problem is. People plug accessories into the cigar lighter instead of one of the accessory ports causing the fuse to blow sometimes.

 

Yep check cig power.