I have a 2000 Sierra with no power to trailer brake light at the plug. Truck brake lights work fine.

There are no actual trailer brake light fuses, so I assume the power runs through the trailer directional fuses (which are really just flashing brake lights).

I have no power at either trailer directional fuse when the brake is applied, so I am wondering if there is any other relay or switch to check between the pedal and the fusebox.

Thanks much for any insight you might have!

 

The trailer connector wiring comes from the the truck brake lights wiring thru a splice at the back of the truck. Trace the wiring from the connector back. Are you using a voltmeter or light to check it at the connector?

 

I am using a light.

So the power for the trailer brake light only runs through the normal truck brake light fuses and not the trailer directional fuses?

EDIT- I just checked a '03 Silverado here at work, and there is power to the trailer turn signal fuses when the brake is applied on that truck.

Could the problem be the multifunction switch?

 

I stand corrected according to my Haynes manual the stop lights for the trailer are fused thru the CHMSL 10amp fuse and for the parking lights thru the TRL PRK 15amp fuse. Both in the underhood fuse center.

 

I will double check that fuse when I get home. Thanks for the info!

 

Is the wiring harness factory installed?

 

I believe it is factory, yes. (I only bought the truck about six months ago)

There is the round plug-in, and I also found a 4-wire flat hook-up tucked up behind the bumper. I had tested both, and they both worked the same (everything works except the brake lights).

When I tried to mess with this a few months ago, I pulled every single fuse and checked them, but I am anxious to get home and look closer at that center stop lamp fuse and possibly the center lamp itself.

 

UPDATE: The high mount center brake light works fine, but I did find another clue from another tip I had gotten.

If I hold the flasher **** on top of the steering column over to the left (with brake applied), I get the trailer brake lights to work. There is a bad connection in that switch apparently.

Looks like it is all a part of the multi-function switch and that is the issue. I am confident replacing that switch will fix the problem.

 

New switch in ($240 for part) and problem fixed.

 

Holy crap $240 for a dam switch.