I thought that Torque Converter Clutch Solenoid was TCC? Anyways, that code after doing the KOER test if you didn't actually toggle it during the test is common, if under normal driving you can turn OD off and it locks out OD, and you can enable OD and it shifts into OD then the switch and associated wiring is fine.
When you did the KOER test did you do the goose test and it passed that? That tests things like the TPS and MAF.
I have never driven a 3.8 powered electronic controlled tranny car before, but my AOD equipped 3.8 car is slow accelerating up hills, but I don't think that is a problem. I personally would do things like clean the MAF and check the normal maintanence things like plugs, last two tranny problems I have had ended up being miss fires from worn plugs. It acted just like TC shudder but when tested it didn't go away like a shudder should, so I looked elsewhere.
I would wait until you get a CEL again and scan it to get the codes, I usually just use a paperclip and count the blinks from the CEL.
97 Mark VIII LSC/Silver/Gray leather
97 Cougar 4.6 Sport/White Opalescent Tricoat Metallic /Gray leather down but not out?
89 Cougar LS 3.8/Oxford White/Gray velour/HG need replaced AGAIN
00 Grand Marquis LS/Vibrant White/Gray velour
63 Falcon 302/black and rust/shed isn't moving
82 F-150/Oxford White/dumb VV carb doesn't pass emissions