Trailer Wiring Harness for 2018 Cadillac CTS Coupe

Updated 04/28/2026 | Published 04/23/2026

Question:

I have a 2013 Cadillac CTS 3.6L AWD premium coupe. I plan on adding 2 rear turn/brake/tail lights to the rear bumper so I need a module to cover turn signals, brake lights, and tail light functions. I prefer plug n play rather than splicing any taillight wiring. Im fine with power and ground from the battery. Which part numbers should I use?

asked by: Michael K

Expert Reply:

Hey Michael! Since you have the coupe you can use the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56044. This is plug and play and then you'll run the power up to the battery like you mentioned. This will combine the turn and brake signals just like on a trailer.

What's the goal for the extra rear lights?

expert reply by: Robin H

Curt T-Connector
(click to enlarge)

Michael K.

4/27/2026

I am adding sequential switchback turn signal/marker/brake lights where the current reflectors in the lower rear bumpers. Just an appearance thing. Adds a little customization thsts all.

Robin H.

4/28/2026

@MichaelK I bet that'll look really sharp on the CTS! If you need anything else don't hesitate to reach out.

Michael

4/28/2026

@RobinH so with the curt c50644 I will have tail/turn signal/ and brake wires coming out of the module to splice and wire into the aftermarket turn signals? I need a tail or running light signal wire, a brake signal wire, and a left and right turn signal wire. There are 4 wires coming from each of the turn signals I am wiring in. 1 os ground obviously.

Robin H.

4/28/2026

@Michael that is why I mentioned it at the end. You will have tail/marker on the brown wire, right turn/stop on the green, and then left turn/stop on the yellow. If you want to connect the two wires from the added lights, turn and brake, to the corresponding yellow/green that works. If you want to separate it out you have to add an additional converter to split the signal on the harness # C56196. This keeps your vehicle wiring protected because you have the powered module with the # C56044 and you still avoid splicing into the vehicle wiring. You do have to splice into the Curt wiring. Also, we only have these converters for incandescent lights. Outside of that, the only option is to tap into your vehicle wiring directly.