Frustrations... Express Van trailer wiring issues

[curtis73]

Wiring up the trailer plug and brake controller on the 06 Express AWD "Candy van" was pretty straightforward... no thanks to GM's complete lack of consistency in the wiring. You might have wires... or not, you might have fuses, or not. You might have circuits in the fuse panel, or not. You might have a GM round plug-n-play adapter, but only if your van came with the factory 7-pole connector.... and all of this is WITH the tow package.

What I got was pretty lucky. I had the blunt cut wires under the dash for the brake controller and the blunt-cut wires in the rear frame pocket for the trailer connector.

Good news: Everything is in and I can now tow with lights and brakes. Bad news: no matter what I do, the red/blk wire at the back doesn't have the 12v+ it's supposed to for aux/charge. Wiring schematics show that the power flows Batt > Fuse 13/50 > X88 trailer connector (blunt cut). Just battery, fuse, then to the back. No relays, no BCM/ECM trigger, nothing. It doesn't even show that it goes through any connectors or bulkheads. Verified all fuses good and verified all fuse sockets have power. I read somewhere about a blue and red wire taped up near the fuse box? Is that a thing?

Before I go doing surgery on 18 feet of wiring loom to find a break, is there something I'm missing?

 

[tyler.armijo]

I mean it may be the field mechanic in me but instead of digging into the harness and possibly damaging other wiring why not just run a single wire as cleanly as possible from the last point you have power to the rear plug? It would save you a lot of headache in my opinion


Sent from my iPhone using Tapatalk

 

[curtis73]

Well, finding the last point of power would require digging into the harness. Good idea, and I did give thought to running a nice 6ga for a rear battery pack anyway, but it would be nice to have the trailer plug working in the meantime.

The last known point it has power is in the fuse box. Then it disappears into a wire loom and exits at the back.

 

[NevadaLover]

Did you check to see if both fuses are in and good?
If they are and you have power on the wires near the fuse box then it's a game of hide and seek to find where the wires are broken, around here the most common problem is cottontail rabbits eating the wires, somewhere they can hide and chew at their leisure, usually on a cross-member or near the frame, good luck!

 

[curtis73]

Both fuses in and good, both visually and tested zero ohms. Both sockets tested and have 12v at the pin. Red/wht works fine and powers the brake controller. Red/blk the power just disappears somewhere.

Thanks for the different schematic. The one on GM upfitter is not as depictive.

 

[NevadaLover]

Sorry to hear that, it may seem like a P.I.T.A. but chasing the wires to find a bad spot isn't really that bad, usually you can see where the damage is and fix it pretty easily, Good luck.

 

[Climber Rob]

I had the same issue on an older truck. I just ran a separate wire from the fuse box and spliced it into the harness at the bumper.

 

[curtis73]

Here's hoping. Initial inspection shows that I basically don't get to look at anything without a pretty in-depth excavation. I get about 2 feet of wire loom before it disappears into the boxed frame. Then, unless it becomes unboxed beside the fuel tank, I don't have access to it again until beside the steering column. I could undo the wires at the back and possibly pull the whole thing out the front but then I don't think I can get it back in there, nor do I know if that wire loom carries other circuits at other points along the way.

Cross your fingers for me.

 

[arveetek]

I read somewhere about a blue and red wire taped up near the fuse box? Is that a thing?

Yes, that's a thing. On the pickups of that vintage, GM did not attach the 12V + battery wire to the stud on the front of the fuse box under the hood; the wire was taped to the harness; you had to remove the wire from the wire harness, and attach it to one of the 12V + studs on the front of the fuse box. I am not sure if the vans were the same way.

Here's a video showing the wire on a 2009 Silverado, just FYI:


Casey

 

[yfarm]

On my 2011 Raptor the charge wire at the plug was not active from the factory, you had to insert a relay provided by ford in a plastic bag in the glove compartment in the specified location in the fuse box to activate the charging circuit. Why?

 

[tinbasher]

Yes, that's a thing. On the pickups of that vintage, GM did not attach the 12V + battery wire to the stud on the front of the fuse box under the hood; the wire was taped to the harness; you had to remove the wire from the wire harness, and attach it to one of the 12V + studs on the front of the fuse box. I am not sure if the vans were the same way.

Here's a video showing the wire on a 2009 Silverado, just FYI:


Casey

i just did this on my 2009 chevy, one wire was for the brake controller power and one was for charging the trailer battery while driving

 

[curtis73]

Good to know. My wire for the brake controller is already hooked up. I'll go digging for the charge wire today.

 

[1stDeuce]

Yeah, I'll second popping the shroud off the fuse center and having a look a the studs. I'd bet there's a red wire taped back to the harness that needs to be dropped on the stud. The pickups come missing that fuse too, with a red "+ BATT" cover over it... At least you must have the fuse...