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Brake lights constantly lit on tail lights?
My right brake light and turn signal went out in my Deali. I replaced the fuses and they work again, but when the brake fuse is in my brake lights on both my tail lights and constantly on like someone is pressing the brakes, but my 3rd brake light isn't on. Anyone have any idea what's wrong??? I have to keep my fuse out just so I can drive my car cause they stay on even when they key is out of the ignition.
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RE: Brake lights constantly lit on tail lights?
I had an old car where I was able to replace what was called a brake switch. It was nothing more than a button that was depressed when the brake pedal touched it. I have no idea if cars still use these simple switches, nothing seems to be simple anymore. But if you have a broken switch, or maybe even a bad brake relay (if there is such a thing), possibly this could be the solution to your problem. Electrical issues are the devil, to be sure!
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RE: Brake lights constantly lit on tail lights?
Not the brake switch. The new gm trucks have a different brake switch. When you press on the brake it puls a bracket that's mounted to it sending a signal to light the brakes. I unplugged this, and the lights are still on so I dunno... Thanks for the help though
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RE: Brake lights constantly lit on tail lights?
Is there such a thing as a brake relay in the fusebox(s). The manual should show it. Just a thought.
[IMG]local://upfiles/13808/D2CE21F8FCA643CCAE22E26EBCAE795F.jpg[/IMG] |
RE: Brake lights constantly lit on tail lights?
The power for the brakes comes from the BCM. With key off, try unplugging the brown connector at the BCM. If the brakes go out, then the fault is with the bcm, or brake switch harness leading to the bcm. If they don't go out, then there is a short to B+ somewhere to the back. The brake circuits are pins 1 and 2 in the brown connector
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RE: Brake lights constantly lit on tail lights?
Where is the brake control module? And if there is something wrong with that, what would I need go replace. Same thing with the pins in he circuit, how would I fix the problem? I guess I still don't know what to do if it's one of those problems. Thanks, this will be a good start and help :)
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RE: Brake lights constantly lit on tail lights?
BCM = Body Control Module. It is under the drivers side of the dash
The brake switch that is being used in new vehicles, are normally closed switches. Which means the contacts are closed when the pedal is noy pressed, and the contacts open when the pedal is pressed. By disconnecting the switch, you made the BCM think the the pedal is depressed. Disconnect the switch, and place a jumper wire into pins c and d. orang\white and purple. See if the lights are still on. If not, you have a bad switch. |
RE: Brake lights constantly lit on tail lights?
If it's the switch, why does the CHMSL still seem to work?
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RE: Brake lights constantly lit on tail lights?
Shark, he said that the CHMSL doesn't come on at all. Good point though...Patry, does the 3rd light work when you hit the brakes?
I am starting to think there is a problem in the BCM, and just thought of something, Try d\c the battery for a minute in hopes that the BCM will "reset" itself and turn off your brake lights |
RE: Brake lights constantly lit on tail lights?
Yeah disconnected the battery already, didn't do anything.
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RE: Brake lights constantly lit on tail lights?
Does the third brake light work properly?
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RE: Brake lights constantly lit on tail lights?
Yes my chmsl still works fine
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RE: Brake lights constantly lit on tail lights?
shawnvw: You're right, I misread what he was saying, but if the CHMSL is out and the brake lites are on, then something isn't right. They must not use a common circuit. Might be a lead for the tech to look at.
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RE: Brake lights constantly lit on tail lights?
i just noticed your running the esky taillights.......Are you using a converter?
Are you able to troubleshoot with a multimeter (or worst case a test light)? |
RE: Brake lights constantly lit on tail lights?
I took my esky lights off, this is with my stock Denali lights.
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RE: Brake lights constantly lit on tail lights?
Follow my earlier post to diagnose this down a little further. The left,right, and center brake light all have separate outputs from the BCM. If the 3rd light is good, then i am more inclines to think it is either a bad BCM, or a wiring issue where the brake lights are shorted to B+
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Did you ever find the fix to this issue?
Sorry for asking after all this time but I'm having the exact same problem and I've been trying to fix it for a while now. |
2011 suburban with brake lights always on
I have a 2011 Chevy suburban and I had the problem with the lights constantly on. After a little research I found out the brake switch is the usual suspect so I changed it. That did absolutely nothing. Upon closer examination I found one of the 4 wires leading to the brake switch cut at the plug that connects to the switch . Put it back together and it works fine now. It was not easy to troubleshoot because the plug looked normal you need to remove the tape that wraps around the 4 wires leading to the plug and pull the wires one by one to find which one is cut,take apart the plug and re solder the wire back in place.
I hope this helps some of you,it almost drove me nuts trying to find what was the problem. |
Hey Gr1000k....I have the exact same issue in a 2009 Silverado. Just wanted to ask how you took apart the plug. I see no other way but to cut the other 3 wires. Thanks for any help you can send my way. I have been all over the internet looking for an answer and just discovered the broken wire tonight, after 2 brake switches of course.
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This thread was a big help, but ultimately what was wrong was SO STUPID!! trailer controller is mounted on dog house. And driver had one of those smelly Christmas tree's looped on the slider. JUST ENOUGH to trigger the brake lights. Crazy thing is, we've had allot of fuse boxes cause electrical issues, on GM trucks. So, I ordered a new one, installed it, and of course did not fix the problem.(did what I thought was a thorough diagnostics, beforehand)
Not only did it NOT fix the brake lights, it was only running on like 4 cylinders!! 12 DTC's WTF??? Removed it to check pins, to see if any damaged during installation. All good. Reinstalled the old box and it ran perfect. Then driver came back and said windows would not work. Ugh!!! Pulled window switch to check for power. All Good. Re-installed switch and BINGO, windows all good. Glad this one is gone...till next time at least. JT City Of Winter Park Fleet Maint. |
Anyone figure this out as I came home last night with my wife' truck doing this exact thing
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I followed a pickup this morning (GM) that the 3rd brake light was flashing with the right turn signal. It was confusing as ____. lol
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Originally Posted by Gr1000k
(Post 323603)
I have a 2011 Chevy suburban and I had the problem with the lights constantly on. After a little research I found out the brake switch is the usual suspect so I changed it. That did absolutely nothing. Upon closer examination I found one of the 4 wires leading to the brake switch cut at the plug that connects to the switch . Put it back together and it works fine now. It was not easy to troubleshoot because the plug looked normal you need to remove the tape that wraps around the 4 wires leading to the plug and pull the wires one by one to find which one is cut,take apart the plug and re solder the wire back in place.
I hope this helps some of you,it almost drove me nuts trying to find what was the problem. |
I bought my 07 Suburban LT a few months back and didn't noticed it was missing the top bulbs on the taillights, I have the same issue with the brake light staying on only on the taillight, third light on top of tailgate works as it should, took it to the dealer and they told me it was the engine compartment fuse box, and of course they charged me almost $400 just to tell me that, so I bought a new one and replace it myself, and still the same, I tried everything you guys suggested and the only was they turn off is either by unplugging the fuse at the side of the dashboard or unplugging the connector at the BCM, by the way, the light bulb has two filaments, brake light and parking light and they both stay on, would it be fair to say is the BCM? thanks in advance.
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Bad grounds will do the same as both filaments can light up through feedback from a poor ground.
Poor grounds are the most common problem. |
By any chance anybody has a wiring color chart to able to follow the ground wire from the tail light to the BCM before I attempt to replace the BCM? thanks
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Originally Posted by Noesito73
(Post 484001)
By any chance anybody has a wiring color chart to able to follow the ground wire from the tail light to the BCM before I attempt to replace the BCM? thanks
According to my 2011 manuals the ground wires (black) for the tail lights go to the left frame rail, behind the left rear tire. Look on the left side of the frame. Good luck |
I checked the ground cables coming from both tail lights and everything is ok, also based on the way they are wired I hardly think that could be the issue, I followed the ground cable from the frame up to the taillights and the same cable works for every other bulb, comes in on the first one and back out to the next until the last one on top which is the one I have issues with and also there are separate grounds for each side which also eliminates my issue since this problem is on both sides, so at this point does anybody think it should be safe to replace the BCM ?
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Use an electronics cleaner / lubricant in the BCM connectors first. Fretting corrosion in GM connectors is common before replacing a BCM. BCM most likely will need programming.
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Originally Posted by Noesito73
(Post 483868)
I have the same issue with the brake light staying on only on the taillight, third light on top of tailgate works as it should,.... the only was they turn off is either by unplugging the fuse at the side of the dashboard or unplugging the connector at the BCM, by the way, the light bulb has two filaments, brake light and parking light and they both stay on, would it be fair to say is the BCM? thanks in advance.
Do the lights stay on when the headlights are turned OFF? What happens when you unplug the PRK LAMP relay in the underhood fuse block? |
Originally Posted by a55bruce
(Post 484555)
Which fuse are you removing to get the lights turned OFF ?
Do the lights stay on when the headlights are turned OFF? What happens when you unplug the PRK LAMP relay in the underhood fuse block? The one that says STOP LAMPS They stay ON when the headlights are off They stayed ON when unplugged the PRK LAMP relay https://cimg0.ibsrv.net/gimg/chevrol...49b3cb2a4c.jpg The one that says STOP LAMPS |
Also I noticed something else today, after I unplugged the PRK LAMP relay and nothing changed, I unplugged the fuse to turn them off so I could touch the bulb to remove it and the top filament stayed on but not really bright, like if it was dimmed , I pulled the relay again and plug it back on and they went out
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Originally Posted by Noesito73
(Post 484759)
The one that says STOP LAMPS
They stay ON when the headlights are off They stayed ON when unplugged the PRK LAMP relay If they are still lit, there has to be a cross-over in the wiring harness, connectors, bulb sockets, etc. Is there a trailer brake controller that's compounding the issue? Check the trailer plug (backside) for corrosion, mud, etc. There is full time power in the trailer plug (pin E ) that could be the source of the leakage power. Try pulling fuse 68, STUD-1.
Originally Posted by Noesito73
(Post 484760)
Also I noticed something else today, after I unplugged the PRK LAMP relay and nothing changed, I unplugged the fuse to turn them off so I could touch the bulb to remove it and the top filament stayed on but not really bright, like if it was dimmed , I pulled the relay again and plug it back on and they went out
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Originally Posted by a55bruce
(Post 484768)
When you pull the PRK LAMP relay, their is NO path from the BCM to power the park filaments in the bulbs.
If they are still lit, there has to be a cross-over in the wiring harness, connectors, bulb sockets, etc. Is there a trailer brake controller that's compounding the issue? Check the trailer plug (backside) for corrosion, mud, etc. There is full time power in the trailer plug (pin E ) that could be the source of the leakage power. Try pulling fuse 68, STUD-1. That's weird, I got nothing :confused: https://cimg7.ibsrv.net/gimg/chevrol...f7ae91c439.jpg |
Originally Posted by Noesito73
(Post 484795)
I unplugged STUD-1 but is not fuse 68 on my truck is says is 71 but nothing happened, I also unplugged any other fuse that called for trailer lights or trailer stop lights and nothing, and YES there was a brake controller when I bought it, when I discover the problem I removed it and taped the wires under the dashboard and removed the two power wires attached to the fuse box under the hood,
I hope the BCM connectors are labeled. Try disconnecting just the BCM X6 connector, check pin 2 with a test light for this phantom brake light voltage. Other BCM connections: BCM X6 pin 2 L-BU = STOP LAMPS BCM X4 pin 4 RD/WH = STOP LAMPS FUSE BCM X5 pin 24 D-BU = PARK LAMP RLY |
Originally Posted by a55bruce
(Post 484809)
Sorry about that, my books are for the 2011, I guess there are some differences.
I hope the BCM connectors are labeled. Try disconnecting just the BCM X6 connector, check pin 2 with a test light for this phantom brake light voltage. Other BCM connections: BCM X6 pin 2 L-BU = STOP LAMPS BCM X4 pin 4 RD/WH = STOP LAMPS FUSE BCM X5 pin 24 D-BU = PARK LAMP RLY The BCM connectors are not labeled other than the color it says nothing else, is there any way to know which one is which ? |
Originally Posted by Noesito73
(Post 485160)
The BCM connectors are not labeled other than the color it says nothing else, is there any way to know which one is which ?
BCM X2, WH, (25pin) BCM X3, L-BU, (25pin) BCM X4, BK, (25pin), pin 4 RD/WH = STOP LAMPS FUSE BCM X5, BN, (25pin), pin 24 D-BU = PARK LAMP RLY BCM X6, PK, (25pin), pin 2 L-BU = STOP LAMPS BCM X7, GY, (28pin) According to my books, X6 is the only connector that has a L-BU wire on pin 2. If this was mine, I'd look for a way to release the wire from the connector (safety pin, paper clip), usually there's a tab or catch holding the socket in the connector housing. This would leave all the voltages and signals going to the BCM except for the brake light wire. If the bulb is still lit then the BCM is probably NOT the problem. |
$20 will get you a one month subscription for your trucks shop manual with the wiring diagrams at alldatadiy.com
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Originally Posted by a55bruce
(Post 485193)
BCM X1, L-GN, (27pin)
BCM X2, WH, (25pin) BCM X3, L-BU, (25pin) BCM X4, BK, (25pin), pin 4 RD/WH = STOP LAMPS FUSE BCM X5, BN, (25pin), pin 24 D-BU = PARK LAMP RLY BCM X6, PK, (25pin), pin 2 L-BU = STOP LAMPS BCM X7, GY, (28pin) According to my books, X6 is the only connector that has a L-BU wire on pin 2. If this was mine, I'd look for a way to release the wire from the connector (safety pin, paper clip), usually there's a tab or catch holding the socket in the connector housing. This would leave all the voltages and signals going to the BCM except for the brake light wire. If the bulb is still lit then the BCM is probably NOT the problem. I released the wire form the connector and the lights are off now, the parking light filament turns on and off with the light switch as is supposed to now, but the brake light filament does not work, the third light still works normal. |
Originally Posted by Noesito73
(Post 487477)
I released the wire form the connector and the lights are off now, the parking light filament turns on and off with the light switch as is supposed to now, but the brake light filament does not work, the third light still works normal.
Final verification of a bad BCM, does pin 2 (without the wire) still have 12 V ?? Yes, Bad BCM No, "Failure to communicate" the testing and results. :confused: (between you & me) :( |
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