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Brake System Fault Warning

1204 Views 2 Replies 2 Participants Last post by  brady000
Hoping to get some help with this...

I have an 09 6.4 Crew 140,000mi, leveling kit, Spartan tuner, EGR delete, Mishimoto radiator, new AGM batteries... Strictly for mileage, I run the 275 tune daily... :laugh2:
When I got the truck the ABS light was lit. I brought to the dealer a few times and they tried to diagnose. After several hundred dollars and several hours of my time, I knew nothing more than when I started.
I bought a code reader, retrieved the codes and after many hours I diagnosed the issue to a broken wire between the frame rails routed to the front passenger side wheel sensor. I have since ran a temporary wire to eliminate the light. No issues since I did that a couple months ago.

Shortly, after making that temporary fix, this current issue showed up. I was towing a 24' Enclosed trailer loaded with ATV's and while driving the "Trailer Disconnected" warning came up. Very shortly thereafter, the "Brake System Fault" warning & Brake Warning Light came up and hasn't shut off since.
I have spent hours trying to trace/diagnose the issue. I checked the connectors on the master cylinder several times. I tried disconnecting the connectors, removing and refilling the fluid, and moving the float switch. No dice!
I removed the trailer connector on the back of the truck and replaced it. There is another brake controller on the dash "Prodigy", I have removed the extra connector at the bumper that is wired to that. No dice!
Within the last couple of weeks I replaced the batteries since one tested bad and the other marginal. I since unhooked the batteries over night and the message still remains.
I have taken it to the local Ford dealer and they couldn't give me a reason the message is on my dash.
While at a local diesel shop for a replacement Mishimoto, I had them try to diagnose it. After being charged for 2 hours, they didn't have an answer but "suspected" the "GEM" module needs to be replaced.
I have spent many hours researching this issue have tried most everything I've read for a solution and am about ready to do something stupid if I can't fix this issue without throwing parts at it.

Besides that, I need to use it to tow a trailer very soon and don't feel safe doing it without a trailer controller.

Any help anyone can give is greatly appreciated! And no matter how or when I diagnose the issue I will post my solution on here to help others...
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I think you have multiple issues here, most likely unrelated. Also, your truck does not have a GEM. The Trailer Disconnected message I assume occurs when the trailer is connected to your truck? You already performed some basic checks and also removed the add on brake controller. The best way to diagnose this is to test the factory TBC system with a brake emulator using a nice tool from Tekonsha that contains a trailer brake emulator and lighting circuit tester indicators. You can leave the tool in the plug and drive around to see if the message stops appearing. If it does it indicates a problem with your trailer brakes or trailer wiring. The tool if I remember correctly was around $40 but I bought mine some time ago - Google it to source it.

Tekonsha - Emulator
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