Brake lights stuck on.

[White Duramax]

Helping a buddy with an 01, his brake lights are stuck on all the time. Already put a new brake light switch on the pedal. Checked the trailer plug for corrosion. Pulled bulbs out of both rear brake lights and the 3rd brake light still stays on. Disconnected the trailer brake controller. The only thing that kills them is pulling the brake light fuse in the underhood electrical center.

 

[blk smoke lb7]

I just had this problem with a 2000 grand prix and the hazzard switch was going bad and had to replace the turn signal and all was good not sure if its the same with your buddys but it sure sounds like it.Maybe Ben will know.

 

[chevyburnout1]

It doesn't have a remote start wired into it does it? Could be failing and back feeding voltage through the brake switch circuit.

 

[White Duramax]

Does not have a remote start. I don't know how the brake/turn is wired with the truck having separate turn and brake lights on the truck but being combined for the trailer plug.

 

[chevyburnout1]

The trailer lighting is combined in the multi-function switch (turn signal switch). The brake light circuit for the truck does not run through it however it is tied into it... Did the lights turn off when you unplugged the brake switch? Try pulling the 'HAZ LP' fuse from the underhood fuse block and the 'TURN' fuse from the panel on the side of the dash. If the brake lights are still on after those two fuses are removed then technically that should rule out the multi-function switch as being the issue.

 

[chevyburnout1]

Edit: Its the 'VEH STOP' fuse you pulled that kills the lights, right? Not the 'STOP LPS' fuse?

 

[White Duramax]

Stop LP fuse is the one that will kill the lights. Brake lights stayed on when I unplugged the brake switch.

 

[White Duramax]

Went and looked at his truck again, the underhood fuse box cover is the wrong one, it is the same as an 05 cover. Anyways I pulled the hazard fuse and turn signal fuses out and it did not change anything. He told me it started when he put his boat in and had to back in the water a ways. I unplugged all of the connectors on the bed electrical block and the third brake light is still on. Does anyone if there is a brake light relay or does it run through the bcm?

 

[White Duramax]

Figured out what happened. Orange wire going to the brake switch got hot and melted into the white wire. Fuse for the brake lights had a 25amp in it instead of a 10amp.

 

[chevyburnout1]

Sounds like there is another issue at hand if there was a 25amp fuse in there and it still melted wires. Glad your making progress though!