1999 Tahoe truck turns on when brake pedal is pressed

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

mhill58

TYF Newbie
Joined
Aug 26, 2024
Posts
3
Reaction score
4
Hey everyone I have an issue I've never seen before on my 99 tahoe, I purchased it and the previous owner told me the brake lights didn't work from a trailer brake short, the 3rd brake light works fine, when I started digging into I ended up replacing the rear light harness and cutting out the trailer wiring, and removed the brake controller, I also replaced the multi function switch as it was broken, when I went to test the brake light with the key off, everytime I press the pedal the truck turns on like I turned the key even though the key isn't in the ignition and if I do turn the key on, the brake lights stay on with out any input for me. I've never seen this before and have no idea what could cause it. Any help would be greatly appreciated!
 

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
20,284
Reaction score
35,271
Location
Willamette Valley
Your brake lights have power all the time. You have a power feed wire, for the brake lights, that is crossed/rubbed thru at an ignition wire, likely in the steering column area, where you did all that work. If you did not have a problem, did some work and then have a problem, recheck your previous work area(s).

Welcome to the forum from Oregon.
 

Doubeleive

Wes
Supporting Member
Joined
Nov 7, 2017
Posts
25,423
Reaction score
37,748
Location
Stockton, Ca.
Hey everyone I have an issue I've never seen before on my 99 tahoe, I purchased it and the previous owner told me the brake lights didn't work from a trailer brake short, the 3rd brake light works fine, when I started digging into I ended up replacing the rear light harness and cutting out the trailer wiring, and removed the brake controller, I also replaced the multi function switch as it was broken, when I went to test the brake light with the key off, everytime I press the pedal the truck turns on like I turned the key even though the key isn't in the ignition and if I do turn the key on, the brake lights stay on with out any input for me. I've never seen this before and have no idea what could cause it. Any help would be greatly appreciated!
go back and check your work again.
 
OP
OP
M

mhill58

TYF Newbie
Joined
Aug 26, 2024
Posts
3
Reaction score
4
Alright I will check it tomorrow and post my findings if anyone has any electrical diagrams of the wiring, it would help alot, thanks guys!
 
OP
OP
M

mhill58

TYF Newbie
Joined
Aug 26, 2024
Posts
3
Reaction score
4
Thank you for that website it helped alot, I finally figured it out after checking every wire under that dash related to ignition and brakes, I got fed up and went to my other tahoe that the frame rotted out on that I'm using as a Daily till I get this other one up and running, and swapped out the switch and there is no issue brakes work like they should. So something is wrong with the multi function switch I purchased more then likely the wires are installed wrong.
 

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
20,284
Reaction score
35,271
Location
Willamette Valley
Yea, that does make sense. You have brake light circuitry routed thru the turn signal system, so the brake lights work when turn signals are on. What I should have caught, was you saying "truck turns on like I turned the key" but you did not say the engine turned over or started. Just that it turned on like you turned the key to maybe accessory or run position.
 

Forum statistics

Threads
131,305
Posts
1,848,691
Members
95,339
Latest member
Emet9213
Top