Trailer Left Side Lights Not Working with Trailer Wiring C56375 Installed in 2018 Chevy Equinox  

Question:

Expert Reply:

It sounds like there is a problem with a relay on the vehicle side. In the fuse panel located in the rear of your 2018 Chevy Equinox check to make sure there is a relay in the K3 location. Wiring harness # C56375 comes with 2 relays and one of them goes in that K3 location. It is for the left side trailer brake light and turn signal.

It is a good idea to check any and all fuses/relays related to the tow package wiring. Under the hood that would be location F28. In the cab check location F03. And in that rear panel check F3, F8, F13, F14, F18, K1, K2, K3, and K4.

Since everything else is working it has got to be one of those.

expert reply by: Michael H

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Bob M.

6/3/2020

Did anyone find a solution for this left side issue? My sister is having the exact same problem on her 18 Equinox, and the dealership has tested it but the trailer works on 3 other vehicles FYI there is a spot for the 2 relays BUT there is no wiring be hide it. I'm a Tech and stumped here

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Chris R.

6/5/2020

Do you know for certain that your sister's Equinox is equipped with the factory tow package? A lack of wiring behind those relays leads me to think that it may not be. If this is the case, she'll actually need the Tekonsha Wiring Harness # 118750 instead, which just plugs in-line with the tail light circuits.

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Bob M.

6/5/2020

@ChrisR Yeah I'm not sure its just weird that the Right side word and the Left doesn't, it does flicker every once in a while as well. was testing it again last night.

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Darren

8/30/2020

We also have same issue. No left brake/turn. The relay in the k3 spot is just for the trailer parking lights. The vehicle came with a spot Behind the bumper to plug in the 4-pin wiring harness. So that tells me it was intended for trailer towing. The build sheet from the dealer also had it listed as having “trailer package”. No trailer hitch though. I don’t understand why the curt wiring harness came with 2 relays. Can’t find any place to plug in.

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Jon G.

9/3/2020

@Darren The relays that come with the Curt T-Connector # C56375 need to be installed in the K2 and K3 locations according to the instructions. If you didn't install both relays then that might be why you aren't getting a those signals. The other this to check is if the 4-Way is sending the signal or not. If it is then your issue is on the trailer side of things and you need to check all of your connections, including your ground connection for that light.

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Charles J.

10/8/2020

Does anyone know how the relays K3, K4 are removed and replaced?

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John A.

11/4/2020

@Darren Im having the same issue. Im an engineer. Tested the output on 4 prong connector on 2018 chevy equinox. The output for the right brake/turn light works as expected, reading around 12-13VDC. The output for the left, if i check it with a meter without a load, i get the same 12-13 VDC. Once i introduce a load (bulb) the voltage drops to 0. Its not the trailer, tried it on other trailers and get the same result. Cant figure out why. Has anyone found an answer for this?

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@john A.

11/6/2020

We found no answers from anyone. We ended up replacing the standard bulb with a “led” and that solved the problem. I’m thinking that the electrical engineers from GM need to answer why they sell a suv with a trailer package but only install the right side with a relay to handle heavy amp load and leave the left side to run off the vehicles standard electrical system that uses transistors that can’t handle heavier loads such as incandescent bulb! If you install led bulbs that will take care of the problem for that trailer.

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Aaron

7/18/2021

@@johnA Installing LED lights worked on my 2021 Equinox

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Gary I.

9/27/2021

@johnA This is the exact problem I am having with my wiring. No power after a load is put on. Right side good. after 30-45 seconds power comes back to plug. Will try LED bulb. Thank You.

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Les D.

10/21/2021

@GaryI As others mentioned, LED's seem to resolve the issue GMC baked into this system.

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