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post #1 of 8 (permalink) Old 02-28-2016, 04:20 PM Thread Starter
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No brake lights

We have a 2013 Terrain and just had the hitch installed. We hooked it up to a trailer and the brake lights won't work. Running lights work perfect but when I hit the brakes they go out. When. Lights are not on and I hit the brakes nothing happens. Any ideas? We tested the grounding but don't see any issues.
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post #2 of 8 (permalink) Old 02-29-2016, 08:15 PM
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Re: No brake lights

Maybe a fuse missing or blown?

Alan
2015 Equinox LTZ 3.6L FWD - Silver
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post #3 of 8 (permalink) Old 03-01-2016, 11:33 AM
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Re: No brake lights

Quote:
Originally Posted by Obxlvr13
We have a 2013 Terrain and just had the hitch installed. We hooked it up to a trailer and the brake lights won't work. Running lights work perfect but when I hit the brakes they go out. When. Lights are not on and I hit the brakes nothing happens. Any ideas? We tested the grounding but don't see any issues.
I would return to where you had the hitch installed.
The right and left brake light wires are the same color but are on different circuits.
They do this because if one brake light circuit goes out you still have the other.
Both wires go from the BCM to the bulbs, the brake light switch is an input to the BCM.
It could be something simple like a bad connection or something is not hooked up right.

2014 Equinox LTZ FWD 3.6L. V-6 (LFX)
GM6T70 Transmission-Gen II(M7W)
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Build Date: Nov. 04, 2013-Delivery Date: Nov. 25, 2013
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post #4 of 8 (permalink) Old 03-01-2016, 12:27 PM
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Re: No brake lights

find out if they tapped into the brake light wiring or used the factory connector in the trunk,

also, are the lights on the trailer normal bulbs or LED?

2013 Equinox LT1 3.6L V6 FWD 88,000
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post #5 of 8 (permalink) Old 03-01-2016, 06:39 PM Thread Starter
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Re: No brake lights

We looked at the voltage and there is no power coming into the brake lights. They look to be wired from the brake lights themselves and the lights are not LEDs. I'm gonna have to call the place I got it done at and ask them to look at it.
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post #6 of 8 (permalink) Old 03-01-2016, 07:21 PM
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Re: No brake lights

Obxlvr13, you didn't mention if your brake lights work after the trailer is disconnected?

Like mentioned, the BCM controls each rear lamp with an individual circuit. Each individual circuit is not fuse protected. If those individual circuits are tapped for additional lights, it's possible this overloaded the drivers in the BCM and burned them out. If this happened, the BCM is fried and needs to be replaced = expensive mistake. It's also not covered by warranty because it's improperly wired up. (Maybe the dealership will cut some slack?) From the factory, GM also wired additional wiring in the spare tire area that is a separate circuit controlled by a relay. These circuits are also better protected by a fuse. This is what should have been used when wiring up for trailer lights.
This has been discussed in this forum before.

Hopefully your brake lights still work when the trailer is disconnected? If your brake lights work, then it seems the BCM is fine. Then I'd highly recommend disconnecting those taps and use the trailer harness like GM designed it for.

Heck, adding the harness for the trailer is really very easy to do yourself. Several members have contributed to a step-by-step in this forum. I'd demand the money back from the installer for the lights not working, then do the trailer harness yourself.
Best of luck.

*Disclaimer: I'm only sharing my opinion. You didn't pay for it, so my opinion is only worth that much, haha.<br />2013 GMC Terrain SLT-1, FWD, 3.6 V6 (LFX), Sunroof
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post #7 of 8 (permalink) Old 03-01-2016, 07:25 PM
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Re: No brake lights

And if your brake lights are not working now with the trailer disconnected, I still wouldn't jump to a fried BCM so quickly. Check the BCM fuses and etc to see if you're lucky there.

*Disclaimer: I'm only sharing my opinion. You didn't pay for it, so my opinion is only worth that much, haha.<br />2013 GMC Terrain SLT-1, FWD, 3.6 V6 (LFX), Sunroof
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post #8 of 8 (permalink) Old 03-04-2016, 12:55 PM
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Re: No brake lights

Quote:
Originally Posted by rbarrios
find out if they tapped into the brake light wiring or used the factory connector in the trunk,
Obxlvr13, just wondering if you reslolved your trailer wiring issue.

I was looking at the factory connector diagram and it states, available with RPO (V92) and (SDD).
It must be a year or trim level thing, I don't have (SDD), trailer hitch with wiring, or (V92), wiring only on the glove box decal.
But I have the square, grey, 4 pin connector with wiring in the left hatch area.

If you are planning to use this wire and connector, verify that you have it.

2014 Equinox LTZ FWD 3.6L. V-6 (LFX)
GM6T70 Transmission-Gen II(M7W)
Crystal Red Tintcoat-Brownstone Leather-(FE2) Suspension-18" Wheels
Build Date: Nov. 04, 2013-Delivery Date: Nov. 25, 2013
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