Troubleshooting Problems With Turn Signals On 2004 Chevy Silverado After Towing Boat Trailer

Updated 03/18/2026 | Published 03/12/2026

Question:

Hello, I have a 2004 Chevy Silverado Z71 and recently started having problems with my turn signal lights. I towed a boat trailer the other day and after disconnecting the trailer I noticed that whenever I use my turn signal Left or Right, all the lights would flash like hazard lights including the Brake lights, Third brake light, Both license plate lights, etc. Also when I press on the brakes with the turn signal on all lights will turn off. I’ve tried replacing the Hazard/ turn signal relay and that did not solve the problem. Any idea what it could be?

asked by: Arturo S

Expert Reply:

Hey Arturo, thanks for reaching out. That symptom usually points to a ground problem in the rear lighting circuit.

When a ground is weak or missing, the current tries to find a path back through other bulbs. That is why everything flashes together like hazard lights and why pressing the brake with the turn signal on causes lights to go out or behave strangely.

Since this started right after towing, the first place to check is the trailer wiring connector and the wiring going into it. Look for corrosion, bent pins, or a short between the turn signal and brake circuits inside the plug. Sometimes moisture or a damaged plug will back feed voltage into the truck lighting system.

After that, check the rear taillight grounds on the frame and behind the tail lamp assemblies. Make sure the ground wires are clean and tight and not rusted. Also inspect the trailer harness if the truck has an aftermarket trailer wiring harness, since those can fail internally and cause exactly these types of issues.

Is your trailer wiring harness factory or aftermarket?

Check those and let me know your findings. I'm happy to help continue to troubleshoot if needed.

expert reply by: Jesse M

Arturo S.

3/16/2026

Thank you Jesse for responding!! I’ll have to check those grounds, the other day I took the tail lights off and couldn’t find the ground. As far as the trailer wiring harness I am not sure if it’s factory or aftermarket, I am the second owner of the truck. But I’ll check it out as well!!

Jesse M.

3/17/2026

@ArturoS Glad to help. Sounds good. Looking back at that model and year, the trailer wiring should be factory since that is what most models came with. It still sounds like a bad ground or shorted wire. I'll be honest though sometimes factory wiring can be hard to troubleshoot. If you have a shop nearby that could take a look that might be easier.

Randy A.

3/17/2026

When I first installed the lights I connected them to the same ground screw from the previous lights. Lights did Not work. I removed ground screw and replaced with a new screw, I also cleaned up the screw hole and sanded the frame to bare metal where the ground screw head would connect to the frame. Lights worked perfectly, nice and bright. Just a note, each rear LED tail light I have individual grounded to the frame.

Jesse M.

3/18/2026

@RandyA Ah yea a bad ground will definitely do it. Glad to hear you got to the bottom of it and got things working. Thanks for sharing!