I have a 2001 GMC Jimmy 4d 4x4. Recently while I was hooking up my trailer to a 4pin connection on the truck it caused a short or something to cause the trucks license plate lights to go out and the trailer 4pin coming from the truck not to work. I pulled the lights out and replaced the bulbs and still no results to the license plate lights. Is there a fuse somewhere that may have gone out or did it short something out? I looked for a fuse in the normal place on the driver side dash and could not see a blown fuse or find one that corresponded with the problem. Would replacing the 4pin connector on the truck help?

SOURCE: 2005 2500hd silverado 4x4 factory

you have to put the fuse in to make it hot

SOURCE: 2000 GMC Jimmy License Plate Lights

That's just the license light housing. You should be able to find one at most wrecking yards. Some NAPA stores have an outlet for these parts as well. Try carpart.com and partschannel.com. Both of these sites are for replacement body parts.

SOURCE: License plate lights do not work.

The licence plate lights are in the same line as your tail light wiring assembly. I assume your tail lights are working or you would have got a ticket for that. The wire is either cut, broken or unhooked from the tail light wires (which usually are brown). If you can not find the problem, you can always run a new wire to the tail light wire from your licence plate wire. Then they should work.
Your other problem is that the license plate ground is rusty & not grounding, which would also not let them work, so you should probably check that first. Rick

SOURCE: 2006 GMC Sierra 2500HD 4WD trailer light connection fuse blown?

under the hood on drivers side right behind the battery. Will be marked trailer light left sand right.

SOURCE: License plate light not working.

check your light fitting units the normally corrode also the wires some times snap on the of side rear inner-wing normally due to a slight bump they break the wires check wires from both side and if one side dosn,t have power just run feeds from that to your non working lights but becarefull for any shorting from the wires when you connect you new wiring