Ok, if you have the HD trailer pkg your wireing should be in place including the plug at the back of your truck with the receiver.Take your voltage meter and check and see if you have power to the centerprong in the plug, this is easy to check because this post stays hot all the time. If its hot, that is where you will get the power that will charge your batteries on your trailer. Don't be surprised if there is no power. GM been counters figure you won't need it even though you got the HD trailering pkg. so they don't provide the fuse. Look in you owners manuel and you at your fuses in the underhood fuse blockand you will find the fuse that the 30 amp fuse that provides power to this post is missing. Try TBC BATT, it's been a while since I have been in the fuse box, you may find that there is a plastic plug in place of on actual fuse.I put in a 20 amp fuse instead of the 30 and it has worked fine. I would rather burn a fuse than wires or worse. This will take care of the chargeing issue. Fuse will cost about $5. Now to get the darn thing to stop. If your truck has the wireing harness pulg-in, you should be looking at the one wire for power to the controller.You may have to look under your dirvers seat for the location that GM entered the cab with the wireing harness which will require you to fish your pig tail under the carpet to make the connection. Look under the truck and to see exactly where GM entered the cab.Hoped this helpedjvp