06 Chevy Trailblazer brake lights don't work..

Ssmgilroy

Original poster
Member
Jun 10, 2012
2
replaced the break light switch, replaced the bulbs, checked all fuses... nothing.. still the two rear break lights don't work. The hazards work, signal works the top break light on the top of the trunk door works... I just don't get it.. anyone please give me some advise..
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
i had this same problem with mine when i first bought her...

did you check all fuses? meaning the ones at the BCM under your drivers side rear seat? before i knew the ins and outs about my truck, i thought i had checked all fuses.. but i only looked under the hood.. so since i still have my warranty, i just took her into the dealer.. turns out that my fuse was blown under the rear seat and it was due to a ground wire rubbing on my frame.. at least thats what the dealer told me.. i never really got up underneath her to see. all has been fine, and its been over 3 years now..
 

Ssmgilroy

Original poster
Member
Jun 10, 2012
2
I did check prior to replacing the break light switch.. Im going to take another look.. Thanks for the quick reply..




Boricua SS said:
i had this same problem with mine when i first bought her...

did you check all fuses? meaning the ones at the BCM under your drivers side rear seat? before i knew the ins and outs about my truck, i thought i had checked all fuses.. but i only looked under the hood.. so since i still have my warranty, i just took her into the dealer.. turns out that my fuse was blown under the rear seat and it was due to a ground wire rubbing on my frame.. at least thats what the dealer told me.. i never really got up underneath her to see. all has been fine, and its been over 3 years now..
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
:Lager Louts: heres to hoping thats it... if not... i know other with more experience and advice will chime in...
 

MAY03LT

Member
Nov 18, 2011
3,422
Delmarva
377dc3b7.jpg


With the brake pedal pushed, can you verify that you have 12 volts on both sides of fuse #34 in the rear fuse box? If you don't have someone to hold the pedal down while you test, you can wedge something between the drivers seat and the pedal.
 

RayVoy

Member
Nov 20, 2011
939
We can narrow this down real fast. If the center brake light works, there is only one fuse to check, #34 in the rear fuse panel.

If the center brake light is out as well, the probable fuse is #12 in the fuse panel under the hood.

If the center brake light works, and fuse #34 is good (check with a meter) the bulbs are probably bad (check 'em with a meter)
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Boricua SS said:
... it was due to a ground wire rubbing on my frame.. at least thats what the dealer told me.....
Must have been a HOT wire, the one going to the bulbs, rubbing on the frame. The ground wire is at the same voltage as the frame, so that sort of fault would never blow a fuse. Just my pedantic (Sheldon Cooper) side talking. :biggrin:
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
the roadie said:
Must have been a HOT wire, the one going to the bulbs, rubbing on the frame. The ground wire is at the same voltage as the frame, so that sort of fault would never blow a fuse. Just my pedantic (Sheldon Cooper) side talking. :biggrin:

:crackup:... i was misinformed by the dealer then... but after my whole experience with the dealer and my new motor recently... it doesnt surprise me of the things they tell me anymore :crazy:
 

miamimike

Member
Nov 30, 2013
1
I have neither of the two lower brake lights working, I have replaced both bulbs, fuse#12 under the hood and fuse #34 under rear seat. Top brake light works but still not others. Any ideas??
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
miamimike said:
I have neither of the two lower brake lights working, I have replaced both bulbs, fuse#12 under the hood and fuse #34 under rear seat. Top brake light works but still not others. Any ideas??
Welcome!!

I assume you have a meter. If not, buy beer and put a sign out on the street: "Free beer if you have a voltmeter and 5 minutes time."

Seriously, you might have a bad ground to the tail light assemblies, but that would also kill off your running lights. Since you didn't mention dead running lights or turn signals, I assume those are OK. And there's a DIFFERENT ground connection for each side, as a it of safety redundancy. So to lose two grounds is very rare.

So it's either the rear fuse block not delivering power to fuse #34, or the wiring from the fuse to the tail assemblies. Check with your meter to see if you have voltage between the light blue (STOP) and the black (Ground) wires at each side in the back.

If you don't have voltage there - check the fuse. If your fuses don't have the nice feature of a top-accessible test point, I recommend you go buy some. They make troubleshooting so much easier. Check each side of the fuse for 12V when the brake pedal is pressed. That will tell you where to look next - upstream from the fuse or downstream.
 

kickass audio

Member
Aug 25, 2012
955
Try what roadie said with the voltmeter, they are so cheap and help so much with troubleshooting so if you don't have one get one for yourself, you will use it more than you know.

I'm surprised that fuse 34 didnt fix it. Do you have the right bulbs for the rear stop lights? I found out myself that they are SRCK and not the normal pinout for the bulb and when I did a LED upgrade on my truck I blew fuse 34 from it shorting out with the led bulb. I like an idiot replaced the fuse 2 times before I decided to check the polarity and sure enough it was the SRCK as others said on here. Such a dumb design but thats car manufacturers for you. The fuse you were putting in could have been broken, I had fuses before that blew but had no visible shows of a break in the fuse and I wouldn't have known it truly was blown until I used my voltmeter on ohms to test resistance of the fuse and sure enough it never got a reading since it was a broken circuit with no continuity.

If those lights come on for the running light I wouldn't think the ground would be bad but it is still a possibility. Have you tried to get a known good bulb or a new one and put it in one of the lights and pull out the bulbs on the other light to troubleshoot it one light at a time?

That is how I would attack it, test the prongs in the light assembly for power and ground. Your pinout of the stop/running light in the rear is the same as this http://www.vleds.com/media/catalog/...f42dca9de82fb58b1/3/1/3157ck_socket_9_1_1.jpg (note: you need to just turn the diagram to the side for your socket, the picture is sideways but it is still the same idea)

Another good thing to test is the resistance of the bulb, follow the same pinout in the diagram above to check out the bulb out of the socket for continuity between the low + and low ground leads as well as the same for the high side. It will be you testing resistance between each side so if you have the socket facing you straight you will test resistance of the top left pin with one lead of the multimeter and then the other lead goes to the top right pin. if you have no reading then you have a broken bulb.
 

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