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No brake lights

Tiny
JOE T-JOE WOOD JR.
  • MEMBER
  • 2007 GMC YUKON
  • 6.2L
  • V8
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
I have replaced the bulbs, relay switch, brake switch and check fuses on side of the dash and the ones under the hood. The top third brake light works but not the ones in the lower housings.
Sunday, July 26th, 2020 AT 2:07 PM

18 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

Power to the high-mount brake light comes from a different source. Since it is working, that tells me the switch is good.

Now, if you look at pic 1, I highlighted two different wires from the body control module. Note the arrow I have pointing up. That goes to the lights that aren't working. The other one powers the high-mount light.

Here is where we need to start. I attached two other pics. Pic two shows the left side brake light and pic three is the right side. Note the wire and color that I circled. Using a test light, I need you to check if there is power in those wires when the brake is pressed.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Do this and let me know the results. Also, I need to confirm that all other lights on the rear are working.

Take care,
Joe
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Sunday, July 26th, 2020 AT 2:27 PM
Tiny
JOE T-JOE WOOD JR.
  • MEMBER
  • 2 POSTS
Found a loose connection on one of the blue wires. Thank you.
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Sunday, July 26th, 2020 AT 5:13 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
JACOBANDNICKOLAS is one of our best! Use 2CarPros anytime, we are here to help. Please tell a friend.
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Sunday, July 26th, 2020 AT 8:08 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Great! Glad to hear you found it. Let us know if you ever need help in the future.

Take care,
Joe
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Sunday, July 26th, 2020 AT 8:38 PM
Tiny
PAULG22
  • MEMBER
  • 1 POST
  • 2007 GMC YUKON
  • 6.2L
  • V8
  • 4WD
  • AUTOMATIC
  • 185,000 MILES
I have the SUV listed above Denali XL. The brake lights only work when the key is in the ignition. Also it will not engage into park. I have to use my e brake so that it will not roll.
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Monday, July 27th, 2020 AT 10:26 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
Hello,

This sounds like the BCM is going out which controls both of these systems. But we should check the fuses first. Here is a guide and the fuse locations along with the BCM location. If the fuses are good I would try a used BCM and plug it in to see what happens. You may need to get it programmed at a shop which will run about $120.00.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Monday, July 27th, 2020 AT 10:26 AM (Merged)
Tiny
RTWELLS
  • MEMBER
  • 1 POST
  • 2007 GMC YUKON
  • 0.5L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
Brake lights stopped working, but the turn signals, flashers and running lights all work. The 3rd brake light at the top is also working.

We've tried replacing the master brake switch on the brake pedal, the combination turn signal switch and the bulbs. All fuses are good, and we don't see anything obviously wrong with the wiring (no corroded grounds or obviously loose wires).

Does anyone have any idea what else this could be? Short of tracing all the wiring to check for broken wires? (It may come to that!)

Thanks in advance for any insight!
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Monday, July 27th, 2020 AT 10:27 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
Tracing wires is fun and it keeps you out of trouble! It sounds like the MIS IGN fuse is out.

Here is a couple of guides and diagrams to help you run some simple tests:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

(Check out the brake wiring and fuse panel diagrams below)

Let us know what happens and please upload pictures or videos of the problem.

Cheers, Ken
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Monday, July 27th, 2020 AT 10:27 AM (Merged)
Tiny
BS3
  • MEMBER
  • 2 POSTS
  • 2007 GMC YUKON
  • V8
  • 4WD
  • AUTOMATIC
  • 40,000 MILES
2007 Yukon, both low brake lights inoperative. Fuse and bulbs are OK. High center rear brake light works; plugs and wires all connected.
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Monday, July 27th, 2020 AT 10:27 AM (Merged)
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Check fuses. High center is independant of lower lights.
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Monday, July 27th, 2020 AT 10:27 AM (Merged)
Tiny
BS3
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  • 2 POSTS
All fuses are ok. Turn signals also work. Thought about brake light switch but the high center rear brake light comes on at the liftgate.
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Monday, July 27th, 2020 AT 10:27 AM (Merged)
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
https://www.2carpros.com/articles/brake-lights-not-working
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Monday, July 27th, 2020 AT 10:27 AM (Merged)
Tiny
JCHANDLER123
  • MEMBER
  • 1 POST
  • 2004 GMC YUKON
  • 2WD
  • AUTOMATIC
My brake lights dim when headlights are onin 2004 yukon xl. When brakes are pressed blinker flashes fast and they take the place of the brake lights when headlights are on. If brake isn't pressed blinkers work fine. Brake lights are dim when headlights are off. Checked all bulbs and fuses and in Feb. This year had rear circuit board and turn signal switch replaced for this problem but still had this happen when it rained outside. I was told may be a bad ground but I don't know where to check this at.
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Monday, July 27th, 2020 AT 10:31 AM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
It should be caused by a bad grounding circuit. Check the grounding points near the taillights.
See the diagram below
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Monday, July 27th, 2020 AT 10:31 AM (Merged)
Tiny
GRANTHORSE
  • MEMBER
  • 1 POST
  • 2002 GMC YUKON
  • 4WD
  • MANUAL
  • 130,000 MILES
I have replaced the left rear brake lights and they still do not work. It was suggested that perhaps it may be a circuit breaker. Where would I find that and is it something I can fix or do I need to take it to the dealership? Or, could it be something else? Any thoughts?
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Monday, July 27th, 2020 AT 10:32 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It may be a fuse but check your ground at lh rear of frame for good connection an dclean ther eis a circuit board on the rear frame in same area so check tosee if power is coming and going through it to light. A test light or volt meter will work.
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Monday, July 27th, 2020 AT 10:32 AM (Merged)
Tiny
RASCALS49
  • MEMBER
  • 1 POST
  • 2000 GMC YUKON
  • 121,000 MILES
The blinker, flasher and brake light don't work on passenger side. Only tail light will light up. The drivers side is fine. I have tried new bulbs and fuses seem to be fine. I have tried new bulbs and fuses but passenger side flasher, brake lite and blinker dont work only tail lite will illuminate.
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Monday, July 27th, 2020 AT 10:32 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Did you check for voltage at the bulb socket or wiring? In the diagram, the brown wire is voltage for tail lamp. The dark green wire is voltage for stop and turn, just not at the same time. Lower Stop and turn are wired through the turn switch.
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Monday, July 27th, 2020 AT 10:32 AM (Merged)

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