I have a 2003 2500hd and I used to have power at the plug in axu. plug but do not anymore. I have checked the connections at the back side of the plug and have checked the fuses under the hood. A friend of my has a 2004 2500hd and he has never had power back at the plud in. We pull the same trailer for the local High School Marching Band. I have looked at the wiring diagram in the GM manual and still have yet to find the problem. Any ideas. Tom

If the large 40 amp fuse under the hood is good then I guess you will need to do a continuity check to see if there is a break in the wire. You could also pull the fuse out and make sure one side of it is hot to verify if power is even getting to the circuit.

Your friend never had power because he never plugged the fuse into the fuse block under the hood.

Look here at picture in post #4: http://www.dieselplace.com/forum/showthread.php?t=197539