Long story. Have an 06 f250 that did not originally come with tbc, but had the coin slot. I bought from famous auction site a complete kit for upfitter switches and separately a used tbc. Then purchased a new master cylinder and transducer for tbc.

The upfitter switches I installed myself and had local mechanic install master cylinder and transducer.

I would get “TBC” fault code because it was not programmed for the controller. So this year I went to dealer to program and this is where problem starts.

Dealer had truck 2 days. They said I had a “bad transducer” and it was still causing fault so they would need to keep it an extra day to fix. Next day, get in truck and it’s hesitant to start at the dealership. (Never before has this happened). Then the tbc fault appears again. The service rep says it tested fine on the “emulator” and if I wanted to I could bring back Monday to re-diagnose. (This was a Friday).

I did not go back. I hooked up trailer Wednesday and went camping for the weekend.

With the 7 pin unplugged from the truck all weekend, Monday upon leaving, battery completely dead.

I did notice that even with the trailer unplugged, the “Gain” button lights on the TBC were still illuminated even with truck off. Then coincidentally or not, the fan for heat/ac/defrost stayed on after I had removed key.

I have read a couple different posts about that issue but want to know if the GEM is related to the TBC or not as it seems pretty strange after 3 years of owning the truck only after taking it to the dealer to get the TBC programmed does it now have a battery draw to the point it goes to 0 volts.

The TBC works but with various degrees of output as evidenced by the power meter on the unit itself. I still get a TBC fault wether I hit the brakes or release off brakes and the constant beep. The tbc will work manually.

I unplugged the TBC at the dash but still have the power drain.

Any help would be greatly appreciated!

 

This may not be of any help too you, but it’s kind of a similar experience. Had a 2006 F350 5.4l that was mainly a plow truck, but try to run it at least once a week when there’s no snow.

Last fall, went out to run it and it was completely dead. Jumped it and it started right up. Got a TBC fault message. Was dead again a few days later.

long story short, the wires in my 7 pin trailer plug had cracked insulation (lot of rust on the truck) and evidently were shorting out and draining the battery. I don’t tow with it, so as a quick fix I just cut the wires out if the plug and capped them off. That solved the battery drain issue.

The tbc fault never went away. I unplugged the controller, but that didn’t get rid of the error either.

so....take a close look at your plug wire insulation by your bumper and see if you see any cracks. Could actually unplug the whole plug about two feet in too (didn’t know that when I cut my wires) to see if that solves the power drain issue

 

So after looking at every schematic I could get my hands on it turned out to be the green wire that feeds both the pcm and evap canister.
The wire was broken under the battery junction box and had open sheathing in multiple places from 12v test lights.
The evap canister was replaced before I bought the truck as it was throwing a CEL. But they apparently missed the broken wire under the hood and opted to run a power wire from the under dash fuse block to the evap canister.
Which altho was not a great fix, it would have been fine and had been up until the dealer programmed the truck for the TBC. Now the pcm was getting power back fed from the canister because they used the blower motor relay fuse when they ran the bypass.
So, I repaired the broken wire under the battery junction box at the left rear of the firewall, removed the bypass and repaired the broken green wire at the evap canister.
Tbc fault light off, CEL off and no more drain on the battery.
Hope someone can use this new found info.
Thanks for your response!