I recently bought a 05 sierra and it has factory trailering package. Problem is I have no running lights when hooking up to my boat. Have brake and turn signals.Seems no power to 7 pin connecter for running light connection.What do I check? Thanks Tom

 

Can you check it against another tow vehicle? if not i'd start with the connection behind your trucks RV7 pulg-in. may simply be an open circuit.

 

Underhood fuse panel on drivers side fender area. Trailer light fuses sould be on the left side of the box. I would start there.

 

check the wireing o the boat trailor check for good grounds also to expand on the rv7 plug if your boat trailor plug is wired a different way then your truck is it wont work right
here is a little reminder i use when looking at plugs also on the back inside of the plug if you take it apart it should have markings where each wire goes but some cheap ones dont
yellow is left turn signal green is right turn signal
other xolors are blue red and white i cant remember what there used for

 

blue is trailer brake, red is battery +, white is always ground.