My grandpa has a 2006 Chevy Silverado, and he has an electric jack for his camper that gets it power from the hitch plug. We tried it in my 2000 chevy silverado and it worked. we then checked to see if his hitch plug had a constant power terminal and we got nothing on the reader, but on mine we got a read? So I'm thinking it might be a fuse problem, but I dont know what fuse it would be... anybody know?

 

maybe a bad ground?
are both vehicles of the same year? maybe it is only good for certain years.
Is it the type where you have to splice into wires
or the type that simply plugs into the rear main wiring harness?
(available at Wal Mart which I have and works great)

 

i take it that you have a factory 7 wire plug and hitch ,if you take a look in the owner's manual on the trailer wiring ther should be a 40 amp fuse that has to be installed to make the twelve volt lead active on the truck .
here is a set of instruction's from e-trailer look at step 2 letter f it will give you an idea were it goes.
How to Install a Brake Controller on Chevrolet / GMC 1999-2006 Pickups | etrailer.com