Does Install of Curt Trailer Wiring for 2024 Volvo XC40 Require Trip to Dealer

Updated 02/25/2026 | Published 02/23/2026

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(47)

$76.26

Hook Probe Circuit Tester

(70)

$14.54

Question:

Purchased the C56355 Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector for our 2024 Volvo XC40 ba see ed on the E-trailer fitment guide. Installed the wiring per the directions and video on the site. The trailer lights did not work. Did some research and found that some required software install on the vehicle to have the lights work properly. Took it to the Volvo dealer and they charged me $286 to tell me that the wiring kit did not include a module for the trailer software to communicate with. Lights still not working and now out the cost of the light kit as well as the cost of the trip to Volvo. What am I missing?

asked by: Chris S

Expert Reply:

Hey Chris, I am really sorry you've been struggling with this and had to spend a lot of money at the dealer and not have it fixed. So the Curt harness part # C56355 is designed to plug inline with the vehicle taillights and use the signals there to create the trailer lighting so it would bypass any factory wiring that would need to get activated. Did you run the power wire up to the vehicle battery and then also ground the white wire?

If you have a circuit tester like the part # PTW2993 test for voltage on all of the wires going into the box when applying the taillight circuits and see if there is then voltage on output side of the box.

expert reply by: Jameson C