7-Way Wiring Upgrade For A 2020 Mercedes-Benz GLS450

Updated 10/07/2025 | Published 10/03/2025

Products Featured in This Question

EcoHitch Stealth Trailer Hitch Receiver - Custom Fit - Class III - 2"

(5)

$523.13

Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector

(1674)

$76.69

7-Way RV Upgrade Kit for Trailer Brake Controller Installation - 12 Gauge Wires

(337)

$96.74

Question:

Hello, Which kit i need to buy for 7 pin wiring harnesses for 2020 GLS450?

asked by: Bogun K

Expert Reply:

Hi Bogun!

To get your 2020 Mercedes-Benz GLS450 set up with a 7-way, you will need to start with a 4-flat. For that, you will need the Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector # C59236. This is a hardwire kit, but it will get you most of the way there.

Next, you will need the 7-Way RV Upgrade Kit for Trailer Brake Controller Installation - 12 Gauge Wires # ETBC7L. This will piggyback off that 4-flat and will get you a working 7-way.

Were you wanting this for a trailer with brakes? And do you already have a brake controller in mind if so? You may need a different kit if you were already looking at a specific option.

expert reply by: Lazer S

ETBC7L Diagram
(click to enlarge)

Bogun K.

10/3/2025

Does 2020 GLS450 has pre-instllaed plug for 4pins connections? Or I need to tap it?

Lazer S.

10/7/2025

@BogunK There didn't look to be an aftermarket wiring harness that plugged into a port, so I would guess there is no port to connect to. It's a bummer, but you will need to splice into your wiring. Have you done this kind of thing before?