I just bought a horse trailer and when I hook it up to my 2006 Silverado, the lights don't work. My trailer hitch and wiring system are new, and the previous trailer owner tested the lighting of

Have you checked fuses? the most common problem is a bad fuse, make sure to check the fuses located under the hood ,check them all, there are light modules and other components that run power to tail lights. also if you use the tow hitch and light hook up and the fuse is bad then also check and see if fuse pops with trailer connected ,if it does then check wiring on trailer lights

check the ground to the trailer this will be the cause of most lights acting funnyit will be the white wire

the braking system is not installed a the factory just the wire from the plug to the fire wall you need to add the fuse and control box

I would think it would have to be a fuse in the engine compartment fuse box. Most likely labeled trailer light or tow light. I wrote a good article on diagnosing trailer wiring problems click here to view.

The 2006 Mazda Tribute w/o factory tow package can't accept a trailer wiring harness. If you install one you will probably burn out the central computer as I did. I had a top notch trailer hitch instaler try three different brand harnesses. I feel Mazda should reimburse me the cost of this car new, as I bought it to tow and was told that it could tow 3500 lbs. False representation!

Sometime around 2000, GM started putting trailering pre-wire harnesses in the vehicle. Your truck may have this harness built in and would greatly simplify brake controller installation. Look under the glovebox and see if there is a wire harness tied off. There will be four wires in this harness, which should be run over to the steering column to use it. Most trailer brake controllers are compatible with this harness.
The four wires in the harness are: Red, 12vdc; black, ground; blue or purple, brake pedal; and brown or white, trailer brake wire to seven pin, four pin, or five pin connector at trailer hitch, if your truck came from the factory with a trailer hitch.
If you are adding the hitch and do not have the four wire harness, the under hood wires from your brake controller are Red, connect to one of the studs under the distribution box cover (the distribution box is on the driver's side against the firewall. Underneath the cover are two large threaded studs which are hot from the battery all the time); and the other wire from your brake controller would have to be run the length of the truck along the frame, tied off in several places, to the trailer hitch connector on the bumper. Follow the directions that came with trailer hitch wiring connector to connect this wire to the proper pin in the connector.
If this has helped you, great, and please remember to vote/comment.
Good luck!

Then the problem is either with your trailer plug in, or the plug in on the truck. Use a test light to figure out which it is.

if you go to a hitch shop they usually have a plug that fit to stock harness for a price but its easier and safer

u must install the fuses for the system in he underhood heavy duty fuse box, it will be marked trailer tow

Is this a 4 way or 6 way connection system? If your truck is wrong, then all factory equipped trailer package harnesses would be wrong, tell your trailer guy...I don't think so.
Is this the first trailer you have hauled?
Let me know, and we will go from there.
REgards,