Troubleshooting Trailer Lights not Working With 2018 Chevy Equinox
Question:
I have a 2018 Equinox with LED tail lights. I recently purchased a trailer and the driver side light doesnt work for turn signal or brakes. The wiring tester shows that the wiring on car is good. I hooked up my 2001 Silverado and the lights on the trailer work fine. Could it be that I need LED lights on the trailer? Could the bulb be drawing too much amperage on just that rear light? It will flash once and then nothing, same with the brakes. I installed the vehicle wiring according to all the instructions and it is a CURT wiring harness. Thanks for any help you can give.
asked by: John B
Expert Reply:
I was unable to find the order number of the wiring harness you ordered from us so I'm not sure exactly what you have but if just the driver side doesn't work it is probably not an overload; there are a number of troubleshooting steps you will need to take.
The first thing to do is take a look at your owner's manual to locate any trailer fuses or relays and ensure they are all there and in working order. Check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals, if not then the issue is with the vehicle wiring.
If the signals going to your harness are okay, you'll need to test the signals coming out of the harness, and if they are correct then your issue is likely going to be with the trailer side wiring. You will also want to check both your vehicle and trailer connectors for corrosion, which can be green or white in color. A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you will need to either replace the plug or clean the corrosion.
You'll also need to make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion. Finally, check your wiring thoroughly to ensure there are none that are crimped, broken or otherwise damaged.
I have added links to a pair of help articles on trailer wiring, including a troubleshooting guide which I highly recommend taking a look at.
Product Page this Question was Asked From
Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Vehicle End Connector
- No Converter
- No Tow Package
- 4 Flat
- Plug and Lead
- Plug-In
- CURT
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Jason M.
4/6/2025
I had exactly the same issue with my 2018 Equinox! I have replaced the existing wiring on the trailer and all the lights! Still the driver side does not work. I checked the Equinox back fuse box, all the fuses are ok. I noticed there was only 1 Turn signal flasher. I was told it operates both the left and right side of the trailer tail lights but I am not 100% sure. The curt harness I installed in the car came with 2 relays, I looked in the fuse box diagram, it shows where they are supposed to go but the it seems 1 socket is not wired! I wonder if the issue is with the Flasher Relay! A GM ISSUE! Cheers