2024 GMC HD no power to trailer power on 7 pin trailer connector

[Swamp rat]

I don’t have +12VDC on pin 4 (AUX 12 V Charging) on my new 2024 HD. I didn’t realize until I recently purchased a new cargo trailer with inside lighting. All other turn and brake lights work fine. Trailer works fine on a buddies older truck. Am I missing something?  I realize the truck is smart enough to not apply signals if no trailer is connected but everything works except I don’t seem to get power to run the inside lights. I found a fuse #84 for ‘TRLR BATT (30A)’ which seems fine. Ideas?  I have apt at dealer in a couple weeks but any earlier help appreciated. 

[MTU Alum]

These trucks with advanced trailering will only send power if it recognizes that a trailer is attached.  

[gemarsh]

What is your definition of "seems fine"?

Did you use a test light on both sides, ohm'ed it out, continuity test or replaced with know good fuse?

[gemarsh]

2 minutes ago, MTU Alum said:

These trucks with advanced trailering will only send power if it recognizes that a trailer is attached.  

Are you referring to the 2024? My 21, 22 and 23 with advanced trailering, the 12v+ at the bumper 7way and in the bed are hot at all times.

[Swamp rat]

This is a 2024 truck. I only continuity tested the fuse. Trailer is attached but the inside trailer lights that are not getting 12v. Have not tried to inspect the wiring harness.  Does anyone’s 2024 work?

[UWSkier]

19 hours ago, Swamp rat said:

This is a 2024 truck. I only continuity tested the fuse. Trailer is attached but the inside trailer lights that are not getting 12v. Have not tried to inspect the wiring harness.  Does anyone’s 2024 work?

I blew that fuse, I think due to a faulty Furrion trailer camera adapter at one point.  That was the only time I didn't have constant 12v to my 7 way.  Just checked again and I have power now.  Truck been parked for over an hour.  Have you verified this with a DMM?

[Swamp rat]

Fixed. Embarrassing. I thought the fuse was good but it obviously was not.

[gemarsh]

2 hours ago, Swamp rat said:

Fixed. Embarrassing. I thought the fuse was good but it obviously was not.

 

Thanks for the update. 

[carkhz316]

On 12/20/2023 at 8:06 PM, gemarsh said:

Are you referring to the 2024? My 21, 22 and 23 with advanced trailering, the 12v+ at the bumper 7way and in the bed are hot at all times.

Same, my '21 is Hot at all times. I used this feed for a cargo light override switch.

[GregNJodi]

Fix for 2024 Chevy/GM 3500 HD Diesel Trailer Braking Problems (w/5th Wheel)
 

Turn off the battery disconnect on your 5th Wheel Trailer to stop electrical backfeed from trailer. Braking should then work. It worked for us.

Edited June 9, 2024 by GregNJodi

[GregNJodi]

 

Fix for 2024 Chevy/GM 3500 HD Diesel Trailer Braking Problems(w/5th Wheel)
 

Turn off the battery disconnect on your 5th Wheel Trailer to stop electrical backfeed from trailer. Braking should then work. It worked for us.

Edited just now by GregNJodi

 

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