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Discussion Starter #1
I have a gooseneck trailer with EOH brakes. My truck ITBC will not work with the trailer brakes. I have read several posts about installing an aftermarket BC. My question is: do I have to bypass the ITBC or can you have both of them working (aftermarket and ITBC). Just wondering if I have to bypass the ITBC or not. Any tips appreciated.
 

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It’s not finding the trailer. The truck ITBC works with my other electric only break trailers without problem. I had a 2012 GMC prior to this 2018 and had same problem and had to use only a aftermarket controller. The breaks worked great with the aftermarket controller. I’m just wondering if you can use both or if I need to only use the aftermarket. Thanks
 

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So your truck braking works fine with some trailers but not with a particular gooseneck trailer. Is that correct? And your previous truck didn't work with this same trailer? When you plug your trailer (the gooseneck in question) into your truck, do you get the TRAILER CONNECTED message?

I don't think you can have both braking systems installed and working at the same time. Thought I had something from Chevy about that but can't find it. There are other posts about this so do a thorough search and see what you find.
 

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So the ‘11-‘’14 ITBC does NOT work with EOH brake systems, but ‘15+ do. There’s an issue with your trailer if it’s not seeing it when you plug in.

If you’re set on installing an aftermarket brake controller, then no, the factory and aftermarket will not work in tandem. Need to unplug the switch on the left dash panel. Also will need to run a new trailer brake wire back to your plug, or at least to the trailer side of the BCM. The BCM activates the brake wire once it sees a trailer, so you can’t use the blue wire under the dash.

IMO, your brakes won’t work even with an aftermarket controller, since the factory one isn’t seeing the trailer. I suggest finding a truck with a known good controller, and see if your trailer works with that truck.


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Try wiring a headlamp or a old brake magnet parallel with the EOH unit. The truck will then see a "load" and turn the ITBC
 

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Try wiring a headlamp or a old brake magnet parallel with the EOH unit. The truck will then see a "load" and turn the ITBC
I spent an entire Saturday on my in-laws 2012 3500 ccdrw fighting this exact issue. Trailer people finally said the gm itbc wont work with their box and only fix is aftermarket brake box. I assume you would you wire it into the wire that activates the brakes?

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To clarify.
'07.5 to '14 ITBC NOT Compatible w/ EOH (must modify trailer)
'15 to '20 ITBC 100% EOH compatible

First thing that I'd check is for trailer B+, at the 1 o'clock position in the trailer plug.
 

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I spent an entire Saturday on my in-laws 2012 3500 ccdrw fighting this exact issue. Trailer people finally said the gm itbc wont work with their box and only fix is aftermarket brake box. I assume you would you wire it into the wire that activates the brakes?

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I ran like this for years till I bought my 2015. Get a sealed round or oval incandescent trailer running/stop lamp, and wire the red wire from the light to the blue (brake wire) on the trailer. Ground goes to ground. I always wired them in right at the hydraulic actuator and zip tied it out of the way.

To clarify.
'07.5 to '14 ITBC NOT Compatible w/ EOH (must modify trailer)
'15 to '20 ITBC 100% EOH compatible

First thing that I'd check is for trailer B+, at the 1 o'clock position in the trailer plug.
You’re correct, you might as well say any factory GM brake controller up until ‘15 HDs won’t work with EOH trailer brakes.


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I ran like this for years till I bought my 2015. Get a sealed round or oval incandescent trailer running/stop lamp, and wire the red wire from the light to the blue (brake wire) on the trailer. Ground goes to ground. I always wired them in right at the hydraulic actuator and zip tied it out of the way.



You’re correct, you might as well say any factory GM brake controller up until ‘15 HDs won’t work with EOH trailer brakes.


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I had a 2012 Duramax 3500 CC/DRW when I got an RV trailer w/disc (hydraulic) brakes. The trucks brake controller was not EOH so it wouldn't work initially, but the fix was to wire into the trailers circuitry a magnet so the trucks brake controller would see that as standard electric brakes. Worked like a charm. Here's an example of a kit, but there are cheaper ways of doing the same thing: Adaptor for non-EOH controller
 

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And with the newer trucks and EOH brakes, if your sitting still and apply the foot brake only, you won't have trailer brakes. But if you use the hand controller they should work. You have to be moving for the foot brake to apply the trailer brakes. Reason that was given was so when stopped at red light your brake pump wouldn't keep working and overheat.
 

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X2. Whenever I do a pull test after hooking up I have to use the levers on the brake controller. When I first got the truck I thought something was broke cause there was no trailer braking with the truck not moving.
 

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Discussion Starter #14
I ran like this for years till I bought my 2015. Get a sealed round or oval incandescent trailer running/stop lamp, and wire the red wire from the light to the blue (brake wire) on the trailer. Ground goes to ground. I always wired them in right at the hydraulic actuator and zip tied it out of the way.



You’re correct, you might as well say any factory GM brake controller up until ‘15 HDs won’t work with EOH trailer brakes.


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Thanks for all the advice. I’m going to try wiring in a running light first to see if that will fix my issue. If not I will try some other tips on here. All great tips!
 
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