How do I remove the fuse panel lid under the dash on a 09 GMC Z-71

It it usually one of the post fuse in the under hood fuse box and they are marked on the lid

Your truck may have had the factory trailer tow package, but that did not come with a wiring connector in that year. There should be a wire harness under the rear of the truck near the center of the bumper with 7 wires of the following colors/characteristics -

Red/Orange - +12V Battery (Thick Wire) From fuse #8 (40A)
Black/Orange - Tail Markers (Thick Wire)
Light Blue - Trailer Brakes (Thick Wire)
Violet/Black - Backup Lights (Thin Wire)
Dark Green/Red - Left Stop/Turn - (Thin Wire)
Brown/Red - Right Stop/Turn - (Thin Wire)
Black - Ground - (Thick Wire)



Under the dash, the brake controller wiring should be -

Red/Orange - +12V Battery (Thick Wire) From fuse #8 (40A)
Black/Orange - Ground - (Thick Wire)
Light Blue - Trailer Brakes (Thick Wire)
White/Tan - Brake Light sense - (Thin Wire)

Hope this helps.

Brake lights run through the hazzard switch. There are known problems with this, and the multifunction switch. You may need to buy a new hazzard switch and OR the multifunction switch. Before you do that, check the pigtail that goes into the brake switch up by the fender, make sure it's not shorting out up there. Happened to me!

If I understand you correctly you have found the blue wire in the chassis wiring but don't know where to hook it up. It doesn't hook up to the truck, you connect it to the blue wire coming from your brake controller. You will have to drill a hole or poke a hole in an existing grommet in the firewall to get the wire through. There should be another wire usually orange or red along with the blue wire in the truck wiring that you hook up to the load center under the hood on one of the unused studs. It is for the charge circuit on your trailers if so equipped. You will probably need to install a fuse for the stud. It should be clearly marked on the load center lid.

The wires would be secured under the rear of the truck. However trailer wiring is only for trailer lighting. Electric trailer brakes require a trailer brake controller.

Look at the harness on the back side of the fuse box under the hood. Pull the fuse cover and the fuse box housing. You will probably have to remove the fender brace. They usually run the wires to connect to in the harness and bend them back into the wrap. Should be orange and blue. You will have to splice into them under the hood and run wires into the cab along with a GOOD ground and the drake switch and a hot fused wire. Look at the owners manual and see if fuse post 1 and fuse post 2 are connected. If not, one will feed to the brake controller and the other to 12 volt power to the trailer... Blue brake and orange to trailer power.
Also look at http://www.etrailer.com/faq-wiring.aspx. Full of useful info.

Strange as it might seem, I had a similar problem with my 2003 Sierra 2500HD. All lights on the truck worked fine, and all lights on the trailer worked fine with the exception of the right brake light. I chased all the obvious possible reasons, (blown fuse, shorted wiring, etc). It turned out to be a sticky relay in the flasher unit in the dash. It is located behind the fuse panel on the left side of the dash, and is accessed through a hole behind the lower panel under the steering column. I removed the fuse panel cover and the lower plastic panel under the steering wheel and was able to remove the flasher unit. I ordered a new one but before I installed, it I checked the old one. The plastic cover comes off easily. There are two small relays for the trailer lights and the one for the right side was stuck in the off position. I freed it up, using a toothpick, gave it a spray of conatact cleaner and re-installed it. It is working fine now. I kept the new flasher unit as a spare in case the problem arises again.

Your problem may not be the same as mine, but at least you will know where the $100.00 flasher is located!

Hope this helps,

Hooty

Did yo check the fuse panel inside the truck its located on the drivers side dash , you have to open the driver side door, in there is a 10 amp fuse that is linked to rt trailer brakes and rt turn signal for the trailer, if the fuse is good there is a black box under the dash located on the floor on the driver side, just to the left of the break, thats where must of the plug in wire harness is for the trailer breaks!

The connector is not under the dash. It is under the driver side seat.

tail lights and brake lights, if u had factory wiring then it will be marked trailer tow fuse.