Can You Use The 3rd Brake Light Logic Module With A 4-Pole

Updated 05/19/2026 | Published 10/25/2021

Question:

I purchase a 20-702 3rd brake light logic module. Can I use a 4 flat trailer connector with product? I dont want to splice into factory wiring of my 2021 chevy silverado.

asked by: Michael M

Expert Reply:

For your 2021 Chevrolet Silverado you will have to splice into the factory wiring to use the 3rd Brake Light Logic Module # PP20-702 to connect the left and right turn signals, along with the green wire.

You can also combine this harness # PP20-702 with a 4 pole harness like the Hopkins Wiring Harness with 4-Pole Flat Trailer Connector # HM38138.

expert reply by: Bryce D

3rd Brake Light Logic Module Install Instructions
(click to enlarge)

3rd Brake Light Logic With 4 Pole
(click to enlarge)

Will

4/7/2024

I am trying this exact setup today. While the break light doesn't blink when the breaks are applied with a turn signal, the light is blinking when I remove my foot from the break with either turn signal on. Is my new module faulty?

Bryce D.

4/8/2024

@Will Not necessarily, what you're describing sounds like a grounding issue so I'd suggest checking the connection of the main ground wire of the trailer wiring harness. You'll want to make sure it is attached to a clean metal surface, or if not you can run all of the trailer wires back to the main ground.

Will

4/8/2024

@BryceD initially tried using the 4 way pin connector but have now tried going straight to Truck frame for ground but still blinks

Bryce D.

4/9/2024

@Will Interesting, it sounds like there may be some back feed from the brake circuit. I recommend installing some a diode # RM-690 on the brake wire to fix it.

Charlie

5/19/2026

I am looking to use a 4 pin connector for a Leer canopy. This module says it will only turn on when brakes are applied and wont be on for running lights. Also, it doesn't suggest it should be used on LEDs. Is there something you would suggest? If this is not going to be a perfect fit I was thinking of running a dual intensity brake light driver to take the brake signals (4 pin green and yellow) from the 20-702, put it into the driver with green wire, and then use the brown 4 pin wire straight to the dual intensity driver to supply constant running lights.