Downloaded FORScan and investigated this issue further.
PIDs to pay attention to here are APP1 %, TCC amp., ABSL rpm, and TP %.
APP1: Accelerator pedal position.
TCC: Torque Converter Control solenoid.
ABSL: Torque Converter slip.
TP: Throttle position, measured by the TPS at the throttle body.
You can see the torque converter slip rpm jump up to above 150 from near 0, then back down to near 0 as the torque converter locks and unlocks. Take note of the TP% and APP% at these points. Notice that there isn't any change in either of the readings which consistently coincides with the TCC activity.
Now take note of the TCC Apply servo amperage. According to
this Sonnax Article, "The TCC solenoid is a normally vented or normally open solenoid. As amperage increases, TCC apply increases and WK pressure drops." It seems to slowly decrease until the torque converter unlocks, then quickly increases to reapply the TCC.
It seems it can be confirmed the locking/unlocking is being commanded by the computer, but I'm not sure why. The TCC will vary pressure to allow very slight amounts of slip to reduce NVH, maybe worn components somewhere cause this to fully unlock the TC when the computer is only intending to slip it slightly. I can't be sure. The TC was also shuddering like hell when this was happening, which tends to happen after you've been running it hard, which I had been doing. I want to look at these same parameters while the TC is locking smoothly, as it is 95% of the time, to see if anything is different. I want to physically monitor the fluid pressure with a gauge as well.
Not sure why the calculated load % is so high, I was cruising along on a flat road with minimal throttle input, as you can see. Also the P1xxx code I mentioned in my last post was cleared when I reset the PCM and hasn't returned, so the jury is still out on what that is. Only trouble code on any of the modules is P0420, which isn't related. Probably.
I must add that I'm very impressed with FORScan. Quite capable, easy to use, free software.