Title says it pretty much. So it's intermittent and always goes away if i cycle the key, turn off/on. I can drive 60 miles and it won't come on, i can drive 15 and it'll come on.. It's fairly random.

When driving in "2H" it obviously doesn't come on(it's not looking at rear wheel slip?)
It only happens in A4WD mode. 4x4 high and 4 Low both work perfectly.

Here's my basic understanding of the system, correct me please if i am missing something:
The advancetrac system is checking tire speed at both rear wheels. If it detects one moving faster it engages a clutch in the T-case that transfers power to the front differential. The signal is most likely generated by 2 hall effect sensors and a "tone" ring located on both the right and left hub/drive shaft.

So, my 2 questions are:
1) what's the most likely culprit? Wiring, abs module(if it handles that stuff),sensor(s), tone ring crack?
Due to how intermittent it is and it doesn't happen when doing anything in particular i'm leaning towards sensor or wiring. Idk though, that's why I am asking.
2) Is there any way to pull the codes from whatever module logs the rear speed sensor outputs for both wheels? There is no CEL and like i said, cycle the key and the advancetrac is working just fine, no ABS light, etc.
If i could read it and find out ex.: Right Rear speed sensor signal lost/out of range". Something to that effect it would cut my troubleshooting by 50%.

Thank you guys. As always, i appreciate any help.
When i fix this i will update it and tell everyone what the problem was so it may help others in the future.

** I have tested advancetrac on loose gravel, it works fine. When the light comes on it does NOT work. Have to cycle key. Very intermittent and happens traveling at varied speeds. Seems to be in straight line travel when i've seen it most. 15 to 65 mph it will occur.

 

Small update which may help:

Trip up to Chicago yielded a surprise: i get the SAME error (minus 4x4 higj flashing) when I'm in 2H mode.
I felt the abs pulsing in town before the error.popped up.
Any ideas fellas (and ladies)?
Thanks
My next step is to have ford scan the abs and find out which of the four sensors is dropping signal,then rip into it. Fun stuff. These little things when buying a used truck....... love it ha

 

That's really the best approach, otherwise you're just guessing.

 

Yea, that's the way i see it as well. I'm not going to find a broken wire, it would be in constant abs failure if that were the case.
Also, i learned that these are not tone rings like an explore/escape or most all other vehicles, they are indeed built into the hub assembly. They're cheap as dirt though at around 65 bucks, and that's with abs sensor/wire. I'll pay ford to run a scan on it and tell me which one. Then? Every single tiny little damn thing will be 100% A ok.
Will uodate this later to potentially help other folks.
Thanks all