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No brake lights and no cruise control

Tiny
MARK2018
  • MEMBER
  • 2001 CHEVROLET SUBURBAN
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 350,000 MILES
Currently no brake lights, no high brake light either. All other lights work. Bulbs okay. Upper brake light is LED style hard to check for bulbs.

Cruise control not working either (not an issue for me but I realize that it is connected to brakes in some way for safety - no brakes = no cruise)

Changed out brake light switch.
White wire has power when brake pedal depressed.
Orange wire has continuous power.
No luck.
Checked fuses all appear okay.

It has factory trailer harness and plug. Testing the tabs on the plug indicate no power at all when lights on or when brake applied.

Also I was at parts store getting brake light switch and had codes pulled, none.
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Sunday, November 18th, 2018 AT 7:38 AM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi and thanks for using 2CarPros.

Since you have power to and from the switch, it is being lost after that. I looked through the wiring schematic and think I know what is happening. There is an additional fuse, after the switch, which sends power to the lights and the cruise control. It is a 10 amp fuse in the under hood junction box. I attached a partial picture of the schematic for you to see what it is I am referring to. First, locate the switch. The orange wire should always have power. Then, when you depress the brake (actuate the switch) the white wire should have power just as you mentioned. Follow the white wire in the schematic and you will see where it goes through another fuse as I mentioned. If that fuse is bad you lost both brake lights and cruise control.

Let me know if this helps or if you have other questions.

Take care,
Joe
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Sunday, November 18th, 2018 AT 6:44 PM
Tiny
MARK2018
  • MEMBER
  • 4 POSTS
Great information! It sounds promising. I looked at the schematic and I see what I need to look for (years as an electronic tech in the USCG pay off now and then). Now I just need to locate the junction block under hood. If you can provide a general location that would be great. I will follow up as I am going to check this now.
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Sunday, November 18th, 2018 AT 7:00 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
I believe it is on the right inner fender. See picture.

Let me know.

Joe
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Sunday, November 18th, 2018 AT 7:59 PM
Tiny
MARK2018
  • MEMBER
  • 4 POSTS
Okay, in the Under hood fuse block Veh Stop has power on both sides of the fuse when brake pedal is applied. I inspected the fuse also and it is good replaced it anyways. No luck with lights yet. I suspect the issue is after the under hood fuse block.
I did check for power on trailer plug (factory item), upper brake light, and the two lower lights with no power showing. I used a test light.
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Sunday, November 18th, 2018 AT 8:33 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Okay, no problem. We are losing power between the fuse and lights. Check for power at the rear lamp junction block located on the cross member ahead of the rear bumper. The power supply to it is a light blue wire. If there is power to the block, out of the block check for power to the brown wire (left brake) and light blue wire (right brake light).

I attached that portion of the schematic and highlighted the wires I mentioned.

Let me know what you find.

Joe
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Monday, November 19th, 2018 AT 5:41 PM
Tiny
MARK2018
  • MEMBER
  • 4 POSTS
Here is a lesson in checking the basics first. I had no power on the upper brake light, or so I thought. I had a hard time getting a good ground but there was power.
So the brake light bulbs (in this model there are two filaments one brake one marker) were replaced and the LED upper assembly went bad also all at the same time.
All bulbs and upper LED were replaced and bingo we have all brake lights back!
What are the odds of all three brake lights going out at once? That is the question I thought of when I started this repair and of which I should have not listened to.
It is why I skipped that step and I will not ever do that again.
Thank you for your time.
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Monday, November 19th, 2018 AT 8:29 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Welcome back.

Honestly, it is not too odd because most times, they burn out one at a time without the driver knowing. It is an honest mistake. I cannot tell you how many times people come in saying they lost low beam headlights only to find they are both burned out. They drive not realizing only one is lit. When it goes, well, you get the point. LOL

Regardless, I am glad you got it fixed. Let me know if I can help in the future.

Happy Thanksgiving to you and your family.

Joe
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Tuesday, November 20th, 2018 AT 5:08 PM

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