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Mystery Wires Under Dash

foxxinabox

New Member
Joined
Sep 11, 2020
Messages
6
Location
Marion, Ohio
Long story short, while attempting to fix my cracked dash and locate the screw I lost, I ended up on the floor looking up. Just to the left of the OBD II socket I ran into a few cut wires coming out the main harness. Mind you, everything on the truck works (to the best of my knowledge) with the exception of the rear park sensors. I've attached a photo (please let me know if it's too large) but the wires are red/black (power wire, I assume, since it is a larger gauge and taped at the end), yellowish-grey, blue, and teal/yellow. I put a zip tie on and tucked them back up under there but sure would like to know what they go to. Thanks.

mystery%20wires.jpg
 
Can you follow them to see where they go? Someone might have added something and took it out when they sold the truck.
 
External trailer brake controller perhaps. ?
 
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I guess I should have added the truck has the factory trailer brake controller / tow package already installed. Doesn't discount something being added later but the DIC doesn't report problems with the system (though I have no trailer to try this with). I cannot trace the wires any further back than where they disappear into the sheathing for the harness (just above the top of the photo) and don't feel lumps from connectors or solders as far as I can trace everything.
 
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Those wires are for end-user trailer brake controller, even if you have one installed from factory. Allows GM to maintain cookie cutter build out as well as provide a way to install an alternative controller.
 
That certainly puts my mind at ease and fits into the whole mass-production for lowest cost / effort thing (thinking poorly designed dashboards here). Should I assume the fuses that are in place for my non-existent rear wiper and seat cooling are likely just there for the same reason and not serving some nefarious function?
 
It's just like most modern vehicles have auto start from the factory but not setup.
 
So, then, it begs the question (which I assume might be covered elsewhere on the site), are there other basic functions on a 2010 Avalanche which are as simple as plugging in a module or switch? Or will anything like that need to programmed in through the BCM?
 
I'm curious does anyone actually use the controller and what do you tow. ???
 
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In some states it’s required by law that all trailers have brakes. Even the smallest utility trailers.
 
In some states it’s required by law that all trailers have brakes. Even the smallest utility trailers.
Thanks sir I meant the built in controller, my other truck came with one but the previous owner had bypassed it already so I never tried it.
 
That’s what I mean. You would hook that up to the trailers electric brakes. If your vehicle doesn’t have that built in, you would have to add one.
Some people bypass the factory installed one for a better aftermarket one.
I use my factory one to control the brakes on my side x side trailer. :cheers:
 
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