no rear brake lights 3rd light ok - Chevy Colorado & GMC Canyon

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Old 06-30-2010, 09:31 PM   #1 (permalink)
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Default no rear brake lights 3rd light ok

perhaps this may help someone else:...

I was having trouble with my rear brake lights not working. I had trailer brake lights and the 3rd brake light worked. used a multimeter on light bulbs they checked ok. unhooked my trailer converter and nothing changed. I did a lot of searching on this site and decided to replace the bulbs anyway; and if that failed i was going to unhook the battery for a few hours.

after I replaced the bulbs everything started working again.

I then did a real close inspection of the old bulbs and found a tiny area on the wire on the bulb that was ARCED
and was not making contact.

you hardly can see it, but it will hang a fingernail, that was the culprit.

this was on my 2008 Isuzu I370 LS
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Old 07-01-2010, 01:34 AM   #2 (permalink)
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Default Re: no rear brake lights 3rd light ok

That is a common failure. That is why we just say to replace the bulbs and inspect the sockets when you have the bulbs out. A cheap way to fix the problem sometimes is to clean the contacts with a pencil eraser. If you do this you might have the problem return at a later date.
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Old 07-01-2010, 08:06 AM   #3 (permalink)
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Default Re: no rear brake lights 3rd light ok

Want to mention that with many GM vehicles, this problem would be the turn signal switch. The center stop light signal comes from the brake light switch itself, where the left and right go through the turn signal switch (so when you step on the brake, and one of the signals is on, the flashing will still be occuring on whatever signal is on). Saw a few really good techs screwing around with bulbs when they should have been replacing the turn signal switch!
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Old 07-01-2010, 06:51 PM   #4 (permalink)
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Default Re: no rear brake lights 3rd light ok

Unlike past cars, our rear turn signals do NOT go through the turn signal switch. The BCM controls them and the turn signal switch just inputs to the BCM. Also our rear turn signals and brake lights are NOT the bulb filaments. This is also the reason you need the trailer light converter to run normal trailer lights that are combination brake and turn signals on the same filament. I do not like it but that is the way they designed it.
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Old 07-01-2010, 07:26 PM   #5 (permalink)
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Default Re: no rear brake lights 3rd light ok

I don't doubt the statement is correct about the BCM. I thought I should point it out in case someone has an older vehicle and have only the center stop light.
I don't understand what's meant by this though:
"Also our rear turn signals and brake lights are NOT the bulb filaments."
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Old 07-02-2010, 05:30 AM   #6 (permalink)
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Default Re: no rear brake lights 3rd light ok

On foreign cars they have one set of bulbs for turn signals and a different set of bulbs for brake and tail lights. Usually the also have the turn signals yellow instead of red. Well we have something similar only they put both the turn signals and the brake lights behind the same red lens. Also they used the tail light filament in both of the bulb sockets. Here is the wiring diagram if you want to see what I mean.

http://www.naskie18.com/colorado/schema ... rt%202.pdf
Take a look at the dark green , light blue, and yellow wires coming in from the left side of the page.

Light blue is for the brake lights, while yellow and dark green run the two turn signal filaments.

A pair of brown leads from fuse 29 and fuse 39 runs the tail lights plus the license plate lights. That's correct two different fuses to the rear tail lights.
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Old 07-02-2010, 11:50 AM   #7 (permalink)
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Default Re: no rear brake lights 3rd light ok

bulbs are dual filament

replace
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Old 07-05-2010, 04:36 AM   #8 (permalink)
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Default Re: no rear brake lights 3rd light ok

Quote:
Originally Posted by Gilly
I don't doubt the statement is correct about the BCM. I thought I should point it out in case someone has an older vehicle and have only the center stop light.
I don't understand what's meant by this though:
"Also our rear turn signals and brake lights are NOT the bulb filaments."
I see I missed an important word..

It should have said:
"Also our rear turn signals and brake lights are NOT the same bulb filaments".
I missed the word "same".

Sorry, I'm a terrible typist and a terrible proof reader. When I went to school only girls took typing. I then spent 33 years in voice / video / data networking, and project management business for a large computer company, so I still never needed to learn to ttype. Anything that needed to be typed went to the word processing department or my secretary.
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