Crazy brake light issues

ryan.g

ryan.g

Hard work, clean livin'
Joined
Nov 1, 2009
Messages
336
This has probably been discussed before but a quick search here and google didn't reveal any answers. Anyways, to the problem. When the truck is shut off, all brake lights, park lights and so on work perfectly. When the ignition is turned on, the brake lights are constantly stuck on. When I am driving and this happens, cruise control will not work. This kinda sounds like a possible brake switch BUT only the tail lights are activated with the issue. The third brake light functions normally. Also, the lights aren't stuck on when the truck is off. What else is there to check? I have replaced both circuit board and all lights. When the 20A Trailer fuse is pulled it will kill the lights. Is there common wiring issues that would cause the lights to pickup voltage from a key on source? Sorry for so much reading and thanks for any help.

Ryan
 
The Body Control Module is the brain that controls the truck electronics, maybe that's going south?
 
Who or what can tell me what is bad? If there isnt any codes or anything will a scanner pick it up? Some of the "could be" things are expensive. I'd just like to be sure instead of throwing money at it.

The brake light in the dash will sometimes come on when the truck is first started on a cold morning but will then shutoff and the lights will continue to stay on.

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Pull the ignition switch out and pop
The cover off. I bet the little contacts are all fallen apart inside.

Not the key lock cylender.
 
Unplug your brake controller and see if they work properly. Had a brake controller go bad on my 06 and had the exact same symptons you are having.
 
Mine did the same thing and it was some of the wires for the trailer plug at the receiver hitch.
 
Mine was the body control module (BCM).
I was able to add a jumper wire but can't remember where exactly as it was more then 2 years ago now.
I think I use the signal from the trailer brake harness to fix it.

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Finally figured it out. The brake switch was bad even though it would work perfect with the truck off.. Seems like the switch failed and stuck on. Glad an $11 switch was it.

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