Power to the trailer plug on my GMC

[Boomer1968]

I have a 2009 GMC 3500 Duramax and pull a 2005 Cardinal fifth wheel,33LE. I can't seem to find which pin is "hot" coming out of my factory installed 7 pin connector. I've been towing this RV for several years and just "assumed" that the truck was trickle charging my RV battery while I was on the road. I have only done single night boondocking on the way to campgrounds so my battery may have been fully charged from being connected to shore power at home before leaving and then being recharged upon arrival at the campground and plugging back in to shore power. Will be traveling out west all summer and will probably be spending some nights not in campgrounds. I do have a generator just in case.

I know I won't get much power back to my RV when traveling but every little bit helps. Thanks in advance for any info. I've been visiting the forum for several years and received much info for a newbie. Now I'm just a better informed newbie.

[TGR]

Some Chevy and GMC trucks have power to their 7-pin trailer connection all the time, while other require the vehicle to be running. My Ford only supplies power when the truck is running.

Many trucks are missing a relay and fuse (found under the hood). You'll have to investigate your truck for the answer.

Check pin 1 to pin 4 on your truck's 7-pin connection with a volt meter or 12V test light.

[jjcook]

If you look at your plug i think it is the first one from the top at like the 1 o'clock position at least that is how my 2013 GMC is wired

[TURBS]

On My 08 Silverado there needed to be a wire hooked up in engine compartment fuse box and a fuse installed.
Wire is not hot when truck is off.


2008 2500hd Duramax
2015 Columbus 320RS
2016 nights camped "0"
2015 nights camped "34"

[RollingDownTheHighway]

On my '14 Silverado a plug had to be connected to the battery. Once that was done, the battery on the TT was getting charged. It's a small wire that was zip tied to a hose near the battery. It was gray

[edt]

Wire needs to be connected may also need fuze added most GM products are hot all the time

[roadking1997]

Depending on the year, but my 2005 Duramax was wired with trailering package, but had a blank in the fuse slot under the hood for the 12v power. Just had to buy a large 50amp fuse and it was good to go.

[Harkerr]

Same with my GMC. I believe it is now hot all the time.

[TxLightkeeper]

I can't say enough good about the guys who hooked my system up for me. They specifically told me they tested the 12v hot line to be sure it was connected and if not, they would have hooked it up. I did find out after the fact that my Titan does not provide power when engine is not running though.

[Tomgky]

I had the same issue with my 2012 Yukon The wire is taped up by the fire wall under the hood. It is red you need to open the fuse box under the hood and hook it up. The fuse (on mine is a 40amp) was already in place all I had to do is buy a metric nut and hook it up. I also found out that if you push the tow haul button while the engine is running it will boost the current to the TT battery.

[rracer5]

Originally Posted by roadking1997

Depending on the year, but my 2005 Duramax was wired with trailering package, but had a blank in the fuse slot under the hood for the 12v power. Just had to buy a large 50amp fuse and it was good to go.

X2....was the same on my 2002 1500HD except all I had to do was install the 40 amp MAX FUSE in the designated slot in the fuse box under the hood. I do know that GM changed things up in later years (as stated in previous posts) but, it's all still in/around the fuse box area under the hood. On my old 2002, when I opened the fuse box cover, the fuse location/slot diagram was under the cover and was labeled "trailer 1" and "trailer 2" I believe.

[Ham Camper]

I have a 2015 GMC Denali 2500 and I did not see any loose wire around my battery. I am getting this correct that I am NOT charging my TT battery when going down the road connected to the trailer? I need to investigate this further.

[rracer5]

Originally Posted by Ham Camper

I have a 2015 GMC Denali 2500 and I did not see any loose wire around my battery. I am getting this correct that I am NOT charging my TT battery when going down the road connected to the trailer? I need to investigate this further.

Check the "1 o'clock" position in you trailer plug to see if it's live (key off or key on). Sometimes they are already hooked up from the factory (trailer package) & sometimes it's left up to the dealer to hook up as part of there pre-delivery prep. but, they don't always remember to do this.

[Herk7769]

As part of dealer prep, the dealer is supposed to connect the power to the under hood fuse block. They did not do so on mine, and many others apparently.

Here is the tech bulletin on how to do it.

The wire is in a bundle taped underneath the battery.
You will need an M-6 nut and a 40 amp fuse (if it is not in the block already - mine was).

[TURBS]

Originally Posted by Tomgky

I had the same issue with my 2012 Yukon The wire is taped up by the fire wall under the hood. It is red you need to open the fuse box under the hood and hook it up. The fuse (on mine is a 40amp) was already in place all I had to do is buy a metric nut and hook it up. I also found out that if you push the tow haul button while the engine is running it will boost the current to the TT battery.

Your passing blinker also goes from 3 flashes to 6!

[rockfordroo]

I installed a relay in the wire to my connector, and installed a switch in my dash so I can kill the power to the connector if and when I want to.

[Ham Camper]

Thanks everybody. I learn new stuff all the time on this forum. I read it every day.

[Boomer1968]

Thanks everybody!!!!!!!

[Mahlstedtd]

Yes there sould be a red wire next to fuse block .Taped to harness. Install on stud at fuse block and check to see if trailer fuse is installed. GM tech.

[18CrewDually]

Check out this youtube video @1:56. https://youtu.be/x0x-2eKSmoM
This was the same for my 2011 Yukon Denali. You may have to hook up BOTH brake controller power wire & the trailer plug charge wire. Both were not hooked up on mine.