Brake lights somehow tied into Cruise Control? - SOLVED

[Steve Waddington]

So, I'm driving today and a guy pulled up next to me and motioned for me to roll down my window...and he told me my brake lights weren't working...neither left nor right nor 3rd brake light. So, I thanked him, came home and checked...all my other lights are working perfectly, but no brake lights.

I logged on here and was doing a bit of reading and searches...thinking it might be the brake pedal switch...but in reading up, it seems the brake light switch is somehow connected to the cruise control. So, I went back to the 'hoe, started it, put it in drive, turned on the cruise control and...nothing! No cruise control indicator light on the dash at all. (Or do you have to be actually driving the car for it to turn on?)

And also curious...isn't that whole turn signal stalk supposed to light up? Mine doesn't. I can't seem to remember if it ever did (sucks getting old).

The 25 fuse in the fuse box under the hood is good...isn't there another fuse somewhere that I should check?

Thanks.

 

[SilverSport]

I don't recall the turn signal stalk lighting up on my 2005 GMC Yukon Denali but I'm old too...

cruise won't work if there is an issue with the brakes as the brakes disengage cruise control if you were driving with cruise engaged...

good luck with your fix

Bill

 

[Marky Dissod]

Cruise Control is designed (at least by GM) to not work if ANYTHING's wrong with the braking system, including the brake light system.

 

[ReaperHWK]

It’s actually this way on my 2006 f150. A faulty 3rd brake light will disable cruise control even back then.

Also it’s very important when upgrading to LED that you use canbus compliant bulbs so it has the same resistance as incandescent or else you’ll have all these problems as well.

 

[Scottydoggs]

dumb question, but have you checked the brake light bulbs yet?

 

[Doubeleive]

So, I'm driving today and a guy pulled up next to me and motioned for me to roll down my window...and he told me my brake lights weren't working...neither left nor right nor 3rd brake light. So, I thanked him, came home and checked...all my other lights are working perfectly, but no brake lights.

I logged on here and was doing a bit of reading and searches...thinking it might be the brake pedal switch...but in reading up, it seems the brake light switch is somehow connected to the cruise control. So, I went back to the 'hoe, started it, put it in drive, turned on the cruise control and...nothing! No cruise control indicator light on the dash at all. (Or do you have to be actually driving the car for it to turn on?)

And also curious...isn't that whole turn signal stalk supposed to light up? Mine doesn't. I can't seem to remember if it ever did (sucks getting old).

The 25 fuse in the fuse box under the hood is good...isn't there another fuse somewhere that I should check?

Thanks.

one thing you can check is reach/look under the dash along the brake pedal and see if the brake switch is pushed up a little, for whatever reason gm designed them so they would move up/down with little effort, a couple times on my 800 I had no brake lights and found if I adjusted the switch downward about a 1/4-1/2 inch (by hand) walla I had brake lights again.
you would think something like the brake switch would be locked into a slot or something but it's not.

 

[GMCChevy]

I don't know if the brake lights still tie into the steering coulm in those but in older GMs they did and the turn signal switch or plug could affect them.

It’s actually this way on my 2006 f150. A faulty 3rd brake light will disable cruise control even back then.

My dad had a Focus wagon that the 3rd brake like corroded and it used that to trigger the solenoid to get it out of park. He was pissed when he was out in the middle of nowhere and found that out. The manual override was defective on them too.

 

[swathdiver]

I logged on here and was doing a bit of reading and searches...thinking it might be the brake pedal switch...but in reading up, it seems the brake light switch is somehow connected to the cruise control. So, I went back to the 'hoe, started it, put it in drive, turned on the cruise control and...nothing! No cruise control indicator light on the dash at all. (Or do you have to be actually driving the car for it to turn on?)

Yes, you have one like Wes said. D891A or 15128874

And yes, when this switch is kaput, the cruise doesn't work either.

 

[Pressureangle]

Rostra has been the OEM cruise control supplier for GM for decades. On any Rostra system where I've had reason to look, they use the brake lamps as a ground signal for the module, which sees +/- change to know whether to engage and disengage. If you have LED lamps, I can't say it's the same. But you might have a look at your brake light fuses- my '04 has separate fuse for L and R brake lamps (as well as separate L and R *trailer* brake fuses...go figure) as stated if the CC sees *anything* out of order in the system it just won't work.

 

[strutaeng]

Check a wiring diagram oncharm.li

On the previous generation of GM, the 3rd light was wired directly through the brake light switch, and taillights wired through the multi-function witch (also through the relay) IIRC.

But I would start with the basics like lightbulbs as previously stated. Also, check your relay. You should hear it click when a helper presses the brake pedal.

 

[Steve Waddington]

UPDATE:
Last night I got under the dash while my girlfriend was behind the Tahoe...and I'd press the pedal and wiggle the switch and all 3 brake lights would go on and off intermittently, so that told me it was the switch that was bad.

Went to O'Reilly today and got the switch...they had 2 different ones in stock, I opted for the more expensive one at 31.00, and I grabbed a set of angled picks to help get the retaining clip off. Glad I did, they came in handy.
Fired up good ol' YouTube and saw a couple of "how to" videos, and just dug in.

Its VERY tight under the dash, especially when you have the same body dimensions as a Sasquatch...but actually the job was pretty easy...well, except for re-installing the retaining clip! Can only get one hand under there and its hard to line it up, and have the fingertip strength necessary to clip it back in place. But I did it. Everything works great...even the cruise control!

Interesting note: when I was removing the old switch...it just came apart! In pieces! I wonder how long I had been driving around with no brake lights? Here's a pic of the old switch:

Oh well...another job done!

 

[Steve Waddington]

OH...I forgot to point out something important about this particular job...and my Tahoe.

My '03 Tahoe is a LT...has pretty much all the options, including the power adjustable foot pedals, and THAT is a big help on this particular job, because everything that is needed to be done is accessed from the right of the steering column. The 31.00 switch from O'Reilly was the proper one for my Tahoe.

On the 'hoes that don't have the power adjustable pedals, the orientation of the switch is different, and therefore the switch itself is different, and cheaper (like 22.00). Its in the same place, but the clip and the way its mounted is only accessible from the left side of the steering column which is a lot tighter and more crowded with stuff in the way.

Guess I just got lucky this time!

 

[GMCChevy]

Thanks for the update. It's nice it was something simple.

 

[adventurenali92]

So, I'm driving today and a guy pulled up next to me and motioned for me to roll down my window...and he told me my brake lights weren't working...neither left nor right nor 3rd brake light. So, I thanked him, came home and checked...all my other lights are working perfectly, but no brake lights.

I logged on here and was doing a bit of reading and searches...thinking it might be the brake pedal switch...but in reading up, it seems the brake light switch is somehow connected to the cruise control. So, I went back to the 'hoe, started it, put it in drive, turned on the cruise control and...nothing! No cruise control indicator light on the dash at all. (Or do you have to be actually driving the car for it to turn on?)

And also curious...isn't that whole turn signal stalk supposed to light up? Mine doesn't. I can't seem to remember if it ever did (sucks getting old).

The 25 fuse in the fuse box under the hood is good...isn't there another fuse somewhere that I should check?

Thanks.

Turn signal stock in my 2006 XL Denali doesn’t light up either. I dont believe any of them do. At least I’ve never seen an -800 with a turn signal stock that lights up.

 

[noodlesandsam2]

Agree - Stalk does not light up, but dash console says Cruise in Green. I think that is what he meant.

 

[Steve Waddington]

Agree - Stalk does not light up, but dash console says Cruise in Green. I think that is what he meant.

Actually, I did wonder if the stalk lit up, but I know now that it doesn't, never did. (I've only owned this Tahoe for 7 years LOL!) I just forgot! And yes, when I turn on the CC now, the indicator does light up on the dash!

 

[Joseph Garcia]

UPDATE:
Last night I got under the dash while my girlfriend was behind the Tahoe...and I'd press the pedal and wiggle the switch and all 3 brake lights would go on and off intermittently, so that told me it was the switch that was bad.

Went to O'Reilly today and got the switch...they had 2 different ones in stock, I opted for the more expensive one at 31.00, and I grabbed a set of angled picks to help get the retaining clip off. Glad I did, they came in handy.
Fired up good ol' YouTube and saw a couple of "how to" videos, and just dug in.

Its VERY tight under the dash, especially when you have the same body dimensions as a Sasquatch...but actually the job was pretty easy...well, except for re-installing the retaining clip! Can only get one hand under there and its hard to line it up, and have the fingertip strength necessary to clip it back in place. But I did it. Everything works great...even the cruise control!

Interesting note: when I was removing the old switch...it just came apart! In pieces! I wonder how long I had been driving around with no brake lights? Here's a pic of the old switch:
View attachment 465901
Oh well...another job done!

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