LMM: Need some help locating harness..

weazel

Member
Oct 5, 2011
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Mason, TX
Where can I find the male end of the wiring harness under the dash that the apps and brake switch harness hooks to? The throttle is plugged and as well as the brake switch, but I can’t for the life of me find where this other ends plugs into..

This is an 08 3500hd 4x4 LMM

Any help will be greatly appreciated so I can fire up this engine I just put back together.
 

Yngdmax92

Active member
Sep 26, 2013
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Are you talking about the plug on the other side of the firewall in the engine bay? It's between the driver side hood hinge and the master cylinder.
 

weazel

Member
Oct 5, 2011
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Mason, TX
I’ve got another LMM truck here I went and compared this one to. Thing is, this other truck has the adjustable pedals, and the one I’m working on now does not.

On the spare truck, the harness goes through the firewall and connects to the harness just behind and below the fuse box.

I went back to this truck and looked, there is a connector, but it’s already snapped into another connector that goes into the wad of wires, and goes through the firewall in a large bundle and grommet.

So I need to search more under the dash I think to find this other end.. and the original owner of this truck that took this harness out doesn’t remember exactly where it’s at, just that it’s on the left side close to the pillar. :angry5:
 

weazel

Member
Oct 5, 2011
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Mason, TX
Wow!

Ok, took all kinds of parts off the dang dash and finally found the dang connector. It’s directly behind the gauge cluster, tucked under the dash piece that pops out from under the windshield, also where the little bulb looking thing that controls automatic daytime lights and what not. Can’t believe the throttle sensor plug goes all the way up in there:confused:
 

Hambone

Always learning
Jan 24, 2016
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Thanks for the RnD
Can you reach it through the radio box out or did you need to remove the whole dash?
 

weazel

Member
Oct 5, 2011
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Mason, TX
Not too sure about removing the radio box, but it was actually way easier than I thought it would be..

If you remove the pillar, remove the dash piece that is directly under the windshield that snaps down into the main part of the dash, remove the knee bolster and follow the small harness that connects the throttle sensor, and brake light switch, it goes up and snaps into another connector that is almost directly behind the gauge cluster. You can’t get to it by removing the gauge cluster as behind it, is a plastic “wall”. But being as you just need to remove three panels, it was way easier than I had thought, now that I’ve seen it lol.