It has been a while since I posted this, and I have some new information, so this original post is being updated on 5/7/2014, at noon.

2006 F-250 Lariat FX4 4x4, 6.0L, 5R110, 45K miles. Truck starts readily and idles smoothly, TBC (trailer brake controller) fault is being displayed in the dashboard information center. The only gauges functioning in the instrument cluster are the fuel level and oil pressure gauges. The glow plug icon will stay lit for a very long time but will eventually go out. All lights, locks, windows, radio, et cetera are functioning. The TBC responds to manual brake application. If the truck is placed into gear, the transmission engages harshly and the engine idle speed ramps up to a higher-than-normal level, and stays at the higher RPM when shifted to any other position including Park.

When beginning to drive the truck, it feels like the transmission is starting off in 2nd or even 3rd gear, or like it is pulling a heavy trailer. The truck does roll freely though, there is no brake drag occurring. Once driving, the engine will drop down to idle speed (It doesn't feel like it is dying or shutting off, just returning to idle), for a fraction of a second, once every 2-3 seconds, repeatedly and predictably. However, if the cruise control is engaged the engine will maintain a steady RPM, no fluctuations. The Tow/Haul switch is not working.

All of the codes that I pull with AutoEnginuity seem to all be components on or related to the CAN bus. I've completed the Ford service manual "Pinpoint Test H" tests (Except for the tests which tell you to substitute the PCM, ABS module, instrument cluster, and TBC, because I don't have any to swap out with.) and I didn't find any problems with wiring resistance.

I have visually inspected as much wiring, and grounds, as I can - front to back, inside and out, checked every CAN bus related connector for moisture, corrosion, pin damage, pushed-out pins, et cetera. I've removed the protective cover from the back of the instrument cluster and visually inspected the circuit board there for any sign of corrosion, damage, cracked or cold solder joints, et cetera. I tested every fuse, swapped alike circuit breakers to different positions, et cetera. I haven't thought much about fusible links, or checked any.

I have either placed it into gear or actually driven it with a variety of individual items unplugged, without effecting any change in the transmission engagement and abnormally high idle speed, or, without any change in the engine speed dropping to idle every 2-3 seconds while driving. Some of the things I disconnected during these tests were the ABS module, one or the other and then both of the instrument cluster connectors, the TBC, and the rear end speed sensor.

Since the instrument cluster gauges are mostly inoperable, I spoke to a cluster rebuilder. The rebuilder said that he had never encountered the drivability issues that I'm experiencing related to a faulty cluster.

Yes, I have taken it to my local Ford dealer! After a $200 diagnostics session they can't confirm the problem but they have a high suspicion of one component. I don't want to tell what it is for fear of tainting the communities advice and insight.

U1900 - ABS/Traction Control, CAN Communication Bus fault - Receive Error
P1000 - OBD Systems Readiness Test Not Complete
P115a - Low Fuel Level - Forced Limited Power
U0155 - Lost Communication with Instrument Panel Cluster
U1900 - Trailer Brake Control, CAN Communication Bus fault - Receive Error
U0100 - Transmission Control, Lost Communication with ECM/PCM A

I've been working on this for weeks now, I really appreciate any assistance.

 

Water infiltration behind the dashboard?

 

Nope, clean and dry truck, inside and under the hood.

I spent 21-years in fire & EMS, lwems. :-)

 

i would look into the P115a code. the the U0155 code.

 

The fuel level is currently about 7/8, it was at about 1/4 when last refueled, and refueled while still running, we've never experienced "limp mode" before.

What were you saying concerning U0155?

I've read a couple of posts where folks had P115a or the "TBC" fault, and it turned out to be the HPOP. I replaced the STC fitting proactively, as well as the stand pipes and dummy plugs, et cetera, about 20,000 miles ago, when we first purchased it from the original owner. I'm thinking more along the lines of an electrical fault than an HPOP problem, considering the group of codes that I'm getting, but I really don't know for sure.

 

i would try to find some pin point trouble shooting for all the codes with communication errors! you have lost CAN communication some where

 

Something is also wrong with your readings. Your ect's and tranny temps are identical.
You would expect the tranny temps to be down around 150-155 or so.
There's no way it would be operating at 192+. Prolonged pulling I can get up to the 180's max.

 

Looks like network issues, can you do a network test?

 

Cheezit, a quick Google search and AutoEnginuity website search failed to spoon-feed me the down and dirty instructions on what is needed and how to perform a network test on the truck. Would you mind telling me a little about how to test the network?

@ r2millers, very true, I'll bet the Torque app transmission temperature isn't to be trusted.

 

Search here for terminating resistors first. Thats a quick way to see if the ic is having issues comming on line. From there I can only tell you what to do with an ids scan tool. Perhaps someone versed in AE can help.
With ids there is a test option that says "network test"

 

I'm back, still needing insight, and have updated the original post.

Anyone seen or experienced my issues before?

 

Ok so when act up and dies or wont start. once again you need to test the terminating resistors.
I see no mention of disconnecting the rcm either

 

2006 model year F-250s with 4x4 and auto are a dime a dozen. With that in mind, I would try swapping out the PCM with a known good PCM from another identical application truck to somewhere and re-evaluate. All of the lost communication codes you list seem to commonly tie into the PCM. I will be honest, and tell you that PCMs very seldom on these trucks but anything is possible, particularly if that driver side battery cover is MIA (it is there for a reason). What readings do you get when you ohm pins #6 and #14 of the data link connector? You should be getting 60 ohms. If you are getting 120 ohms, you have a module offline.

 

Mike... my vote goes to ic droping off the network.
That said 07 pcm should be the same

 

I was thinking that as well Moe, but at least a temporary PCM swap would be a quick and easy test to do. And yes, '07 trucks are the same as '06 trucks. Also too, I don't think any pre-'08 trucks give a s*** if a cluster is present or not, in order to run.