I am having problems with my 7 way and 4 way plugs the 4 way has nothing at all and the 7 wat which is factory also the left turn signal doesnt work nor does the brake light on that side.I checked where the harness plugs in in at the big round connector and there is no power there.Where do i need to start to trace those wires?

 

You probably don't have to trace out the whole harness. I have an 04 and I had to replace the connector on my last two SD's. Most likely, if you follow the wire harness from the plug up to the frame, you'll find a connection up near the spare tire on the left side. You can un-plug the trailer harness there, unbolt the connector from the mounting plate and check it on a bench with a meter. As with my last two trucks you'll probably find the wire jacket has been rubbed against the trailer hitch frame and shorted out. Check your fuses as well. You will probably also find the trailer 7 way connector is full of corrosion. Best is to replace the plug with a new one. This may not be the problem, but it's what I found to be a common problem. I also re-routed the trailer harness so it wouldn't happen again.

 

Check the power distibution box under the hood on the drivers side. Fuses for trailer lighting are in there as well.

If the lights work on the truck and not on the trailer that is where to start. For specific fuse locations check your owners manual.

 

I did that the fuse is good it is only the one side that doesn't work.

 

Did you ever figure out what would cause just one side to not work? My 2001 has the same problem. No right brake light or turn signal.

 

A little something to add.
I had problems with my running lights working intermittently. Turns out the ground in the wirining harness was insufficient for the load. It also affected the brake controller and the brakes, but that'll be another thread. Anyway, I went to a trailer shop and they said the trailer gets it's biggest ground connection through the ball connection. A long story short; My ball was not working as well as it should (your laugh here). I ended up installing a second connection up under the left rear of the bed directly above the brake light. I put in a bolt with a wing nut for the connection and ran a six gauge wire down the support behind the brake assy light and grounded it directly to the frame. It took care of all my problems and you can't even see it's there. I know this is not your problem with your individual lights, but someone else might read this and see where their problem is.
BTW: you guys might have given me the solution to my bent pin in my seven-pin connection problem. Thanks,
Spencer

 

The right and left side on a 2001 are fused separately. In the power distribution box under the hood, fuse #1 is the left stop/turn, fuse #3 is the right stop/turn. Fuse #4 is backup and parking lamps. Fuse #16 is trailer 12v.

Owner's manual can be found here...

http://www.genuineservice.com/genuin...loveboxresults

 

Turned out that my aux back up lamps had blown a fuse...lol

 

Thanks dchamberlin, I checked the #22 fuse under the hood and it was blown. Hopefully when I hit up the parts store in the morning all is well and I am not chasing down a short.

 

So, your aux. ground, Is it bed to hitch, or frame to hitch? I am having some issues, one of which was fixed when I cleaned the harness ground, but cannot get either turns/brakes to work.

Thanks