Brake controller install issues

[afest]

Hello everyone from SD, been using this site for a few years for advice on my 2007 Yukon XL Denali. I’ve had this vehicle for several years and I’ve decided I wanted a break controller. I went with the prodigy P3 part number 90195 from Etrailer. I have a red with black strip, blue, white and light blue with white stripe.
Red w/black stripe= black on controller
Blue = blue on controller
White=white on controller
Blue /white strip= red on controller

The red is from the positive post under hood. I have constant 12v on that.

Blue goes to back and into 7-way. I checked continuity to that and it checked out.

The white is factory spliced into a black in the group of wires under dash and I have continuity to known ground but only when battery is unhooked. Will not ring out when battery is hooked up.

Blue w/white strip has continuity to 4 wire brake switch blue/white harness when unplugged from switch. This is my issue, I have a constant 3.9 volts on this blue w/ white strip wire even when unplugged from brake switch.

My cruise and everything worked fine until I tried to hook the controller up. Now cruise control does not work. I replaced the brake position but it didn’t do anything. Everything I’ve read says that the cold side of the brake position switch should be 0.0v until you press the brake pedal. Mine reads 3.9v then goes up to 12v when pedal is pushed down. If I touch the blue/white to ground the voltage goes away.


I’m at a loss. I feel like I’m chasing the wind at this point. If anyone has ran into this issue I’d greatly appreciate some direction on what to try next. Im leaning towards cruise control module, check the brake lights, remove and clean the 7 way at the back. Possibly a new BCM.

thanks

 

[afest]

Update, when I pull the fuse for the BCM behind the panel on drivers side. The 3.9 volts on the blue w/ white stripe goes away… problem with the Body control module possibly?

 

[afest]

Pic

 

[mikez71]

or your brake controller bad/hooked up wrong? you said cruise was working until you hooked up the blue/white to red wire on controller? And now blue/white has 3.9V?

 

[afest]

or your brake controller bad/hooked up wrong? you said cruise was working until you hooked up the blue/white to red wire on controller? And now blue/white has 3.9V?

Correct, although I did not check the blue/white before hooking up the controller, but the 3.9 v is present all the time even with the controller unhooked. The only way I can get it to go away is by pulling the BCM fuse. I am pretty sure I hooked the controller up correctly as it’s only 4 wires and I checked the other 3.

 

[afest]

Correct, although I did not check the blue/white before hooking up the controller, but the 3.9 v is present all the time even with the controller unhooked. The only way I can get it to go away is by pulling the BCM fuse. I am pretty sure I hooked the controller up correctly as it’s only 4 wires and I checked the other 3.

Etrailer is also sending me a different controller but I’d like to get this voltage to go away before trying a new one.

 

[afest]

Etrailer is also sending me a different controller but I’d like to get this voltage to go away before trying a new one.

I should also mention that I hooked up a scan tool and didn’t have any error codes present.

 

[afest]

I should also mention that I hooked up a scan tool and didn’t have any error codes present.

1 other issue is that the reverse lights will sometimes never shut off. I installed the 10 amp fuse for VEH BCK/UP #15 slot and they will sometimes never shut off. My cure for this years ago was to just pull the fuse and I’ve driven it like that for years and not had any issues like a drained battery.

 

[Fless]

Does your RPO code list show JL1?

 

[afest]

Not that I’m seeing

 

[afest]

Not that I’m seeing

 

[Fless]

Are you following the guide that is linked below for your connections?

Accessories - Aftermarket Trailer Brake Controller — 2007 GMC Yukon XL Denali AWD V8-6.2L Service Manual | Operation CHARM

Detailed repair manual for the 2007 GMC Yukon XL Denali AWD V8-6.2L.

charm.li

EDIT: it looks to me like the connections should be to the 4-wire trailer bundle, not to a junction box. I can't tell from the under dash pic what's going on there.

EDIT2: That Prodigy P3 is a great controller -- I have one and use it.

 

[afest]

Here’s how I wired it. These wires were hanging out and had been cut by previous owner and I mounted the my controller in the same holes they had on mounted in

 

[Fless]

That's a generic wiring drawing for a vehicle that's not wired for the 7-pin trailer connector. Did your Denali come with the 7-pin connector on the hitch? If so, the factory wiring should be there. Unless it's defective, it's the harness to use.

 

[afest]

The previous picture I posted was just showing the BCM fuse I pulled to get the 3.9 volts to go away. I have nothing wired into it. The fuse I’m pointing at is the one I pulled to get the voltage to go away.

 

[afest]

Factory I haven’t added anything on this vehicle.

 

[Fless]

All I can recommend is to find that factory 4-wire bundle and use it to connect directly to the Tekonsha pigtail. Look at the pics in the link I sent from www.charm.li.

 

[afest]

Yeah, that’s what I did, the wires were short because the previous owner cut them short when removing there controller before trading vehicle in. I spliced them in and the blue/white has a voltage when it shouldn’t. I’m leaning towards replacing the BCM or bringing it to a GM dealer to diagnose

 

[afest]

I appreciate your help, if anyone else has ran into this issue of the stoplight wire (blue w/ white stripe) for trailer brake wiring, having a voltage on it when brake pedal was not pushed in, please reach out.

 

[mikez71]

Is your new brake switch bad? Power on that wire with brake switch disconnected?