I knew that line pressures were not available through the Tech 2. My thoughts were to see if the TAP cells might indicate a place where the controller was trying to adjust for something amiss so the cell value there would be out of the range of the other cells??
The picture I posted was from my Yukon at a time when it needed a rebuild. I should have a look again now and see what the values are having had the transmission fully rebuilt.
Having a thought here --- just tossing spitballs on the cave wall, if you will.
I do not believe that the TAP Values are as flexible as has been reported or alluded to here.
They are kinda like LTFTs in that they are only reporting a COMPOSITE TREND, not a happenstance ... right?
This may be leading people to false flags and missing something else, more unobvious.
THEN I think somehow I noticed that the OP was concerned of the transmission being in 4th and TCC L/U at the same time. I wondered about that.
It is not a problem that those can be happen at the same time ---
f'rinstance: the TC can be called in if the transmission thinks it is overheated --- even in 2nd, 3rd and 4th.
► FTR: TCC is NEVER allowed in 1st or Reverse --- for obvious reasons.
If the TCC is locked up under an overheat command --- the, as each shift happens, the TCC is momentarily released to accommodate the shift so you don't swallow your teeth. I nicknamed that release as a "Burp Switch", as the 700R4s had just that type of hydraulic pressure switch to release the TCC at each shift point.
To shift with the TCC locked up is a terrific hit, and it will make a believer out of you if you ever feel it --- as to how much shift-shock the convertor absorbs!
FUN FACT: Old wives' tales would have one to believe that clutches and/or bands slip. They do NOT. Hookup is immediate and the impact is severe -- because those clutches and band(s) cannot tolerate that abuse more than a couple of times before they char beyond usefulness.
Solution? Kill all those old wives and their silly tales.
Overheating of this transmission is maybe 30% caused by the torque convertor ---er:
converting horsepower to torque - and torque into horsepower. Hence - it is a "Torque Convertor" (much like a shock absorber, which work as their name implies: as shock absorbers).
But torque-conversion is not the only high-heat generator in this vehicle --- there's the other 70% of the heat which comes from the TCC.
That 70% worst offender is the damned digitally-applied TCC!
► It is never 100% entirely hooked up, nor 100% released.
► It is always dragging and boiling the ATF off the Kevlar clutch and sending that scorched/scorching fluid into the rest of the hydraulic system to eventually be pumped into an already overloaded engine cooling system.
NORMALLY --- and if the unit is running less than the threshold of what the TCM considers "HOT" --- the TCC may not come on in 2nd, but it
CAN normally lock up if 3rd gear VSS range is held for a period of time --- and I am not privy to whatever the TCM considers a sufficient "period of time" to it.
► I imagine if one were to cruise at 44 MPH, then the 3-4 shift might not happen, since the gate for that seems to be 45 MPH on all of my four 4L60s and one 700R4.
If you ever have your 4L60 rebuilt, have the PWM deleted in that it will then be an analog switch ---> (basically:
ON or
OFF - with nothing in between by percentages --- which are transmission killers!) instead of digital, and then you can feel for yourself just how busy the TCC really is.
FUN FACT #2 Since I have had a rebuild of my transmission to the way I wanted it ... 3" 2/4 band, PWN-Delete, Transco H2 Shift Kit™, hardened drum, 5-pinion straight cut planetary set, S10 torque convertor w/TCC, Corvette 2/4 servo (which I may remove because the 2-4 3" band is so aggressive) and laminated apply pistons, where available --- I have a really hard time getting my ATF up to 185°F towing 3 cords of wood (@3500 lbs) and I attribute that to the PWN-Delete almost wholly.
Ding Dong Transmission School is out for a while. Recess!
.
TJ -- I have grown to love you and your technical expertise with all my heart -- I just think there's something else involved here as these TCC clutches are short-lived, they create a lot of heat and are usually the canary in the coal mine and the first notice that the Direct (3rd gear) clutchpack is dead or dying or slipping badly. 
