2024 HD series No power to 7 pin or in-bed 4 Pin

davidm767 · October 19, 2023

I posted a reply in the MODs forum as well, but I have a question for the bigger group. I tried connecting a aftermarket tail light bar to my 2024 Chevy 2500HD LTZ with the MAX towing package. The problem is I am not getting adequate (really almost no) power to my 4 pin in-bed receptacle nor my 7 pin bumper. I tried running my multi-meter with the hazards on and its not showing a consistent power supply (I am getting inconsistent .05v spikes every few seconds though). For the Bumper I ran a Curt 55384 in-line 4 pin connector, which also doesn't show power. I checked all the fuses in the box and they are good to go. I've read the 2023 post about trailer lights not working on some older trailers as well as LED lights, but I know the 2024 is a different beast from an electrical standpoint. I guess my question is: 1) why aren't the 7 and 4 pins powered? 2)Is there a way to permanently power them if they require a certain load resistance to operate? FYI the bar works great on my Wife's rental Jeep Wagoneer when connected into the 4 pin (displaying a check trailer lights DIC message likely due to the low draw).

Edited October 19, 2023 by davidm767

newdude · October 19, 2023

Trailer lighting control module is in charge. It needs to see the resistance from the lighting on a trailer (or light bar in your case) in order to then power it up. This is also why aftermarket trailer light testers will not work. The dealers have a special tool for trailer diagnostics on these newer trucks that is designed to simulate a trailer (has enough load to allow the lighting module to power on everything) and test all the circuits functions.

You could test this with a Curt 57003 adapter that has built in resistors to light an LED trailer up. 7-Way RV Blade LED Electrical Adapter (Not a Wiring Extension) SKU #57003 for $31.13 by CURT Manufacturing (curtmfg.com)

But you'd probably have to then add a 7 way to 4 way adapter.

I don't know if the Putco bar offered by GM will work (p/n 19418352) but that bar ties into the tail lamp connectors themselves, not the trailer. Putco engineered a plug and play harness for this bar to work that is in that 19418352 bar.

davidm767 · October 19, 2023

1 hour ago, newdude said:

Trailer lighting control module is in charge. It needs to see the resistance from the lighting on a trailer (or light bar in your case) in order to then power it up. This is also why aftermarket trailer light testers will not work. The dealers have a special tool for trailer diagnostics on these newer trucks that is designed to simulate a trailer (has enough load to allow the lighting module to power on everything) and test all the circuits functions.

You could test this with a Curt 57003 adapter that has built in resistors to light an LED trailer up. 7-Way RV Blade LED Electrical Adapter (Not a Wiring Extension) SKU #57003 for $31.13 by CURT Manufacturing (curtmfg.com)

But you'd probably have to then add a 7 way to 4 way adapter.

I don't know if the Putco bar offered by GM will work (p/n 19418352) but that bar ties into the tail lamp connectors themselves, not the trailer. Putco engineered a plug and play harness for this bar to work that is in that 19418352 bar.

Thanks for your quick reply. So it is a load resistance problem, great to know!

It seems even PUTCO's quick connect harness isn't built for the 2024 model (apparently GM changed the light connector harnesses), however the bar you linked does seem compatible with 2024 trucks (albeit at 3x the cost of the bar I purchased). Thanks to you I did find the Curt 57004 7 pin to 4/5 pin connector with a load resistor for LED lights. I'm going to purchase this as a possible work-around and I'll connect it to the in-bed 7 pin receptacle. If it does I'll solder the reverse wire into the 5th pin port. Hopefully this will be a permanent solution to my current (pun intended) problem.

Thanks again!

Edited October 19, 2023 by davidm767

davidm767 · October 20, 2023

I can now confirm the Curt 57004 7 to 4/5 pin connector works great with my LED light bar. I imagine this also might be a work around for those who have issues with their truck not recognizing their trailer.