Solution to Allow Trailer Running Light Circuit to Function on 2019 GMC Sierra 1500

Question:

my trailer running lights dont work but brake and signal do. I tested truck plug with volt meter, no power running light pin. Fuse is good. brought it to dealer he said system is pulse width modulated and he had to connect a bulb that draws more than 55ma to test power at pin and it worked said I need a load resisters series to get lights to work. took truck to trailer guy, he tested truck plug and said it was good. I went home connected old headlight bulb to old 7 pin cord only connecting to running light pin and ground. turned headlights on and it worked. tried connecting trailer again and found lights went on for 1 sec so I turned lights off then back on and running lights went on for 1 sec again, every time I turn headlight switch off then on lights will go on for only 1 sec then nothing. maybe I need the load resister but doesnt make sense

asked by: Dom S

Expert Reply:

The trailer wiring on the newer trucks like what you are experiencing on your 2019 GMC Sierra 1500 and the new Ford trucks with the "smart tow" package are proving to be challenging for reasons like what you found where the truck doesn't want to show a trailer connection.

The easiest solution you'll have will be the 7-Way Trailer Adapter # C57003 which was designed for German vehicles towing trailers with LED taillights that has load resistors built into it. Basically you'd install this adapter into your current 7-way, your trailer into the socket, and then you'd have load resistors on the circuits which will allow them to function.

expert reply by: Jameson C

Ken Z.

2/7/2020

Recently purchased a 2019 GMC Sierra 1500 and although the running light do illuminate the Furrion Observation Camera does. Dealer tells me that this smart trailer system is designed to fluctuate volt causing the camera not to function. Will the 7-Way Trailer Adapter # C57003 remedy this problem too. The dealer has no answers short of rewiring the trailer.

Jason S.

2/10/2020

The 7-Way Trailer Adapter for VW, Audi, and Porsche Towing Trailers with LED Lights # C57003 or the Trailer Connector Adapter w/ Lamp-Out Sensor Bypass - 7-Way RV to 7-Way RV - Vehicle End # 20142 have integrated resistors for vehicles needing power for LED Lights. I haven't heard of that issue with the Furrion Camera system but the # 20142 is what I would try first. Let me know if you need further assistance.