Check trailer brake lights

kodiakdenali · December 1, 2020

I get a DIC message every time I brake with my trailer attached. my trailer has all LED lighting on it, is it possible the brake lights on the trailer don't draw enough current for the truck's computer to detect them as working? if so, how exactly can that be? it's the 21st century...GM didn't design the truck to understand LED trailer lights?

The lights do work, I tested them with the trailer lights test feature, which is just awesome, they all work as expected.

Anyone with a similar experience or should I ask the dealer to take a look at it?

MG386 · December 1, 2020

I have non LED on my trailer and no problem, but following to see since I was thinking of changing them out for LEDs...

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kodiakdenali · December 1, 2020

2 minutes ago, MG386 said:

I have non LED on my trailer and no problem, but following to see since I was thinking of changing them out for LEDs...

Sent from my Pixel 4 XL using Tapatalk

hopefully this thread can get some answers for you, its honestly really annoying. its not just a one time thing. every time you touch the brakes that message appears, and stays up until you press dismiss manually or release the brakes. next time you brake, it comes back.

if it really is an issue with LEDs not drawing enough, I'll have to add some extra brake lights or a load resistor just to get rid of that.

no messages about running lights or turn signals which are also LED, says nothing about reverse lights which my trailer does not have.

Enough · December 2, 2020

2020 Silverado LT. Sport Trial boat trailer with LED lighting. I have no issues with messages in the DIC.

Not many lights on the trailer. One 3/4" amber clearance light on each side, one combination taillight each side, and one 3 light center clearance in the rear crossbar. No reverse lights.

Have you had a chance to check the grounds on the trailer taillights ? Sometimes it's a pain the get good grounds on aluminum trailers.

Thanks for the reminder about the trailer light test feature. I completely forgot about it and have never tried it. I wonder if after the test, the feature has to be manually turned off. If left on it would probably cause issues. Just throwing that out there since I have never used the test.

DiverRick · December 2, 2020

9 hours ago, kodiakdenali said:

I get a DIC message every time I brake with my trailer attached. my trailer has all LED lighting on it, is it possible the brake lights on the trailer don't draw enough current for the truck's computer to detect them as working? if so, how exactly can that be? it's the 21st century...GM didn't design the truck to understand LED trailer lights?

The lights do work, I tested them with the trailer lights test feature, which is just awesome, they all work as expected.

Anyone with a similar experience or should I ask the dealer to take a look at it?

I'm in a 2019 with the trailer app, and have recently replaced all the lights on my trailer with LED's. No problems reported, and everything checks out ok and work ok.

ChinkySuperman · December 2, 2020

18 hours ago, kodiakdenali said:

I get a DIC message every time I brake with my trailer attached. my trailer has all LED lighting on it, is it possible the brake lights on the trailer don't draw enough current for the truck's computer to detect them as working? if so, how exactly can that be? it's the 21st century...GM didn't design the truck to understand LED trailer lights?

The lights do work, I tested them with the trailer lights test feature, which is just awesome, they all work as expected.

Anyone with a similar experience or should I ask the dealer to take a look at it?

I have 5 different trailers and they all have LED tail lights. I had an issue with only one, and it turned out to be bad grounding on trailer.

kodiakdenali · December 2, 2020

Thanks for all the feedback! looks like I've got some investigating to do.

if you had a bad ground on the trailer, how did you detect that? the lights on mine all work as expected when using the trailer app.

I have had wiring issues on the trailer before, its pretty new but somehow the wires for the brakes were routed incorrectly, they were cut by a piece of the suspension one day causing brake failure. fortunately it was an easy fix, but there is precedent for it being a trailer problem.

ChinkySuperman · December 2, 2020

5 hours ago, kodiakdenali said:

Thanks for all the feedback! looks like I've got some investigating to do.

if you had a bad ground on the trailer, how did you detect that? the lights on mine all work as expected when using the trailer app.

I have had wiring issues on the trailer before, its pretty new but somehow the wires for the brakes were routed incorrectly, they were cut by a piece of the suspension one day causing brake failure. fortunately it was an easy fix, but there is precedent for it being a trailer problem.

It was driving me nut b/c if I had the hazard lights on, the troubled light would flash, but if I tried to use it as turn signal, it wouldn't flash. It really doesn't make sense, but in the end I decided to use my multi meter and check the for continuity between the ground mounting joint and a good known ground location.

Moend · December 3, 2020

Intermittent electrical issues are buggee to find. I would start with checking any possibile wiggle points. 7/4 pin connector. Have someone wiggle it while applying the break and so on

2020Z71LTZ · July 15, 2022

My trailers have incandescent bulbs for tail, turn, brakes, but LED's for markers. Getting the message, "CHECK TRAILER BRAKE LIGHTS" when the brakes are applied. The light test checks out but dealer says it not a warranty issue. Service GM Service Bulletins suggest owners install resisters on wiring. Has anyone done this yielding good results?

Edited July 15, 2022 by 2020Z71LTZ
more information added for clearity