OK, and for those of you with an Ultra Gauge, if it is not plugged in all the way, or is unplugged and plugged back in quickly, what kind of display do you get?

As for snake oil scanners, anything (including two tin cans and a string) is better than the Rover temperature gauge, which is only one step ahead of smoke signals (tail-pipe kind, not Native American).

 

I just re-filled the tranny about 4-5 weeks ago (yes topped off when running). Tranny shifts fine with the exception of these 1-off events. The ultraguage works out fine for my needs, especially right now when working thru cooling scenerio's. I have no regular or pending codes.

Now back to my original question?

 

Unplug and reseat connectors for tranny ECU and XYZ switch? Skint wire on harness that is rubbing (shake the harness)?

 

The U-G if not plugged in all the way will not display data.
I suppose if the plug were loose while bouncing down the road it could wiggle good connection and bad connection and it may read "err".
Mine will show "err" on the RPM after I shut the engine off as the U-G stays on for 30sec after you turn off the ignition.
All others show the last known input and "freeze" there until I turn the key back on.
As for the OP's problem, I have no idea.
Maybe his U-G is bad?
Try it in another car.

EDIT:After unplugging from the data port or unhooking the battery the U-G will show "scanning" on the display as it finds the protocol for the truck and then it picks up where it left off.
I was worried about loosing all of my data when I replaced my alt, I did not, it was all right there.