'06 F250 "TBC Fault" no start/stumble issue


ExploreNW

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Good morning all!
I got my F250 5.4L back just a week ago from getting its 4th fuel pump & 3rd FPDM. I couldn't get it started yesterday, and today when I went to go fawk with it (basically hammer the key & have someone spray starting juice 'til it at least stumbles) it stumbled to life after 30 seconds of cranking, then the in-dash display showed "TBC FAULT ... Check Gauges" while it beeped at me. The second I press the gas pedal she'll shut right off. As of now it is not displaying any codes on my scan tool and all live data looks normal. Starting fluid has very little effect if any, so it may not be getting spark 95% of the time.

Work it had done in '18:
Spark plug recall/SP-509 conversion
All coils
Fuel pump #2 & FPDM #1
All wiring to pump and driver overlayed
New throttle body
New FRP sensor

Work it had done in '19:
Fuel pump #3 & FPDM #2
PCM/EEC-IV Failed - Computer Replacement
Brakes & rotors
New injectors bank 1

Work done in '20:
Fuel pump #4 & FPDM #3 (OEM this time, $705 total)

This is my work truck. It's a lemon, it has been nickel-and-diming our small business since we got it. Up until this incident it has always been professionally maintained for this reason. It's pretty well done and ready to be replaced but we need to get another 6 months out of this thing before we can go get an '18-19 diesel. Has anyone else on TRS fought these issues before? All I could find is issues pertaining to the 6.0 diesels, irrelevant to my gas motor.
 


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acsnowrider

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You didn't mention what your mileage was on the 2006-- And was all this work done at the same place?? Almost seems as parts are just being changed/thrown at it!!!
 

adsm08

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Does your scan tool have the ability to do a network test on the vehicle? Is the odometer coming up, or is it a series of dashes or zeros in the box?

The symptoms you describe paired with the TBC fault message make me think there is a CAN issue.
 

ExploreNW

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Mileage is roughly 190,000. 100k of those miles are my doing with regular maintenance on time. In '19 I moved to another state entirely so the work hasn't been done at the same place. I agree with you, I'm sick of having parts thrown at it and paying for a truck no one actually trusts enough to use. All of the mechanics it's seen are ASE certified, I make sure of that. The work done in '18 was at a Napa shop, '19 PCM from the stealership, and '20 a new highly regarded shop up here in Washington.

The odometer does come up and the gauges self-test like normal. I found a diagnostic video showing the "smart" fuse box itself going bad and how to check for that, so I'm going to grab some wire & see if that's it.

adsm08 you mention CAN, I don't doubt it. It has had a few wiring patches done already. TBC fault is likely a connection to the trailer brake controller which gets used about once a month & worked fine last week.
 

adsm08

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Just for fun, unplug the TBC and see if it will start.
 

ExploreNW

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Scan tool only reads live data, it can't do a network test. Its a generic ~$150 Walmart unit.

If I had less carb stuff and more EFI stuff I should get a real USB tool & software suite but alas I stick to the world of gettin' at em with screwdrivers, buckets & zip ties
 

adsm08

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Scan tool only reads live data, it can't do a network test. Its a generic ~$150 Walmart unit.

If I had less carb stuff and more EFI stuff I should get a real USB tool & software suite but alas I stick to the world of gettin' at em with screwdrivers, buckets & zip ties
Got a laptop? A laptop and $50 will get you almost the full array of dealership diagnostic abilities.
 

ExploreNW

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More screwin' with it learned me some stuff:
Wiring from the IFS down to the pump & driver is good. The IFS is also still good. Pump runs with 12v leads from battery so it ain't getting the juice or it is intermittently.
Next thought, fuel pump relay - so here I am digging through the manual & I can't see anything that looks remotely close to an FPR. There's a fuse, thats it, the other relays in the pax compartment and under hood all do other stuff. I swapped the PCM relay with another one for grins and it still didn't run any longer than it took to drain the pressure out of the fuel rail.

Pulling the TBC did about as much as expected, nada.

Edit, JUST got codes out of it! Or, one. P0191 Fuel Rail Pressure Sensor Low. It's a part I replaced in '18 but this code is more an indicator to a problem rather than the problem being the sensor itself.
 

adsm08

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Ok, so PCM seems to be working. But power is not passing to the fuel pump.

I can't find anything definitive in Ford, but it is possible the FP relay was integrated into the Central Junction Box and not serviceable. I know the F-150s were that way that year.

If that's the case it is actually a pretty simple matter to wire around that and install a serviceable relay outside the junction box. I've had to do it to a Town and Country before.
 

ExploreNW

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I can't find anything definitive in Ford, but it is possible the FP relay was integrated into the Central Junction Box and not serviceable.
This... This right here. My Haynes manual only mentions a fuel pump relay once and does not mention a test procedure - only mentions replacing pump & FPDM and suggests testing/replacing wiring. In 4A-4 the only mention in the entire book of a fuel relay says the pickup models have the relay mounted way up behind the radio. Who the hell designed these things... are fuel pump relays not a regular wear item anymore? Seems that Ford's silence on the relay and a lack of mentioning it in the service manuals is why the techs replaced 4 pumps & 3 FPDMs (they couldn't all last 10,000 miles or less before blowing, I hope) as there doesn't seem to be a diagram for the whole circuit.

So I bled the clutch on my Ranger instead & hit the parts store looking for the J-box. It's out of production so I got a relay breakout box instead. If i could find a wiring diagram for this thing before snipping wires it shouldn't be a hard job to do.

If Ford's gonna do stuff like this though... Next time I buy a work truck I'm gonna shave my beard off & get a little pink dress. I deserve to look pretty when I get fawked :thefinger:
 

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[QUOTE="ExploreNW, post: 1718730, member: 104265
Wiring from the IFS down to the pump & driver is good. The IFS is also still good. Pump runs with 12v leads from battery so it ain't getting the juice or it is intermittently.
Next thought, fuel pump relay

Edit, JUST got codes out of it! Or, one. P0191 Fuel Rail Pressure Sensor Low.
[/QUOTE]

You mentioned "good wiring" I'm going to presume, you determined this by "ohm" testing the harnesses, from one plug to another. But, did you check "pin fit/drag"?? I found, over many years, that the biggest cause of electrical issues, were from "over probing", meaning somebody prior to my check out, had installed/shoved to large of a probe into the connector ends, when testing the electrical curcuits-- You MUST verify that the pins, both male and female, fit correctly, with sufficient "drag" to provide circuit completion. I made special filament ends/adapters for this. Also, finish testing the circuit, by sending voltage thru it while DISCONNECTED, and verify the circuit carries the load by using a "light"--I used a separate car battery, and a simple 12 volt bulb,-This will verify if the circuit will carry a load. Also, closely inspect the terminals for clean surfaces. You indicated a low pressure code, on the rail, and I am thinking you have "voltage drop, prior to your fuel pump. And just a reference, (don't know if yours fits this bill, having no wiring schematics), but many later Fords, had non serviceable fuel pump relays, mounted into the SJB--The ones that I did replace, required a entire box.
 

Shran

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Weird that the TBC Fault pops up. Mine does that constantly but it was because the gauge cluster came out of another truck that was programmed with a trailer brake controller - I didn't have one, snagged one from the junkyard, trailer brakes work great but still get the fault on the dash. I found that there is a sensor present in TBC equipped trucks in the brake master cylinder that provides some function to the TBC module - if you add a Ford TBC to a truck that didn't have one originally, you have to add that sensor and a different master cylinder and have the gauge cluster reprogrammed. I have confirmed that the message will go away after that.

Not saying that this has anything to do with your deal but maybe it has at least something to do with that message on yours. Faulty sensor, wire, ground, TBC module, etc maybe be making it throw that code.
 

ExploreNW

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You mentioned "good wiring" I'm going to presume, you determined this by "ohm" testing the harnesses, from one plug to another. But, did you check "pin fit/drag"?
I did ohm-test everything from IFS back. Only because I know where the IFS is. I do take those OEM weather-tite connectors for granted however. The connection on the top of the tank itself is brand-new. I have narrowed it down to a relay issue - which is a massive problem...

Not saying that this has anything to do with your deal but maybe it has at least something to do with that message on yours. Faulty sensor, wire, ground, TBC module, etc maybe be making it throw that code.
I'll investigate the sensor - but I agree it shouldn't shut down the truck. I use the TBC about maybe once every month and could live without it.

So, this relay - I cannot find any wiring diagrams for a 2006. I need to know if it is embedded in my PCM or soldered into the back of the in-cabin relay box, but most importantly, I really need a wiring guide. Haynes and Chilton's both have hundreds of wiring guides but neither have the circuit I need and neither am I having any luck with Google finding one that's not for a power smoke, an expedition, or the very different return system on an 04. Looks like its possibly also behind the radio. I'm rather disappointed that Ford could neither make this information available in the owners' manual or to the publishers who wrote both of my service manuals.

Does anyone know where I might be able to find this simple wiring diagram? It's a one-hour fix or less at that point...
 

acsnowrider

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ExploreNW:

Seems, from memory, and it ain't what it use to be, but I went round and round looking for F/p relay in this model, and it wasn't behind the radio, but part of the SJB/CJB. I think adsm08, is correct! It was located on the board, about two thirds down it, and the size of a Monopoly Hotel, not large, like the replaceable ones. And just for info, ran into several with "cracked" circuit boards, creating nasty intermittent issues. Hope this helps:)
 
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ExploreNW

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I think adsm08, is correct!
Confirmed! Got the CJB out. It's in there. I found a sketchy site & grabbed the wiring diagram for the fuel system. Did not want to pull 57 solder joints, nope, not that comfortable. Not ready to trust one from a JY or Ebay yet either but I would not rule out a cracked board. Power lock remote quit a few weeks ago followed by the latest TBC issues. For the temp fix I just need to go get a $10 relay breakout box now.

Here's what to look for:
- Fuse 40 / FPR Feed / Hot all times
- IFS feed line DG/YE to switch side
- Hot Start/Run - Coil side
- Batt Ground BK/WH - Coil side

This will probably cause CAN issues and/or make the PCM feel all sad and alone.

I'll find a way to scan & post my wiring diagrams when I'm done if this is the fix. Looks like the 04 return system is the last year to have the replaceable relays. In 05 Ford went to a returnless fuel rail on the 5.4.

Edited for clarity - LB/OG wire feeds FPDM not CJB.
 
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