2004 silverado 4wd

Hi-

I'm having trouble with the trailer circuit on my truck. When I hook up my boat both trailer trailer lights flash when you turn on the right turn signal. Also only one brake light works. Everything functions properly on the truck.
When we hook the boat up to 3500hd Chev the trailer lights work how they should. Any ideas? The truck is totally stock with no mods.
Thanks in advance

Hi-

I'm having trouble with the trailer circuit on my truck. When I hook up my boat both trailer trailer lights flash when you turn on the right turn signal. Also only one brake light works. Everything functions properly on the truck.
When we hook the boat up to 3500hd Chev the trailer lights work how they should. Any ideas? The truck is totally stock with no mods.
Thanks in advance

One or the other is wired wrong for the trailer plug.
Did your 2004 come with the trailer plug?
Brown wire for tail lights.
Yellow wire for left turn.
Green wire for right turn.
White for ground.
Get a 12 volt test light and go to your trailer plug on truck.
If the round type trailer plug in the prongs inside it should be marked on the inside
TM = tail and park/brown wire
LT for left turn and RT for right turn and GD for ground.
If just the flat wire plug match the colors on wires to what is what.
If that works out you will need to rewire you trailer to match it.

Thank you so much for the response! I thought that too but if you take the trailer out of the equation and plug the 4 flat (says Delphi on it)into the round socket then troubleshoot with a test light it gives the same result as the trailer.
I bought the truck brand new and everything is factory original. My buddy says it was screwed up at the factory and another buddy says there has to be some sort of conversion box somewhere. I see now evidence of this while searching thru the truck and tracing wires. The truck looks like new and nothing is damaged. Any ideas or am I barking up the wrong tree?