Re: one time tranmission warning
I believe it's just a communication problem, or the wiring harness to the trans might have a wire with a broken or worn casing causing a short, and hence the odd warning light. For it to flash the same code however might mean it's sensor related.
In other cases (mostly with Dodge products) of engines of similar years, the IAC, or TPS can cause a transmission to shift erratically. Both sensors, the Idle air control and throttle position sensor are found on the throttle body. Both are about $50 or less, so shop around, stay away from dealer parts as they'll be $100 each, if not more - I made that mistake.
Another thing is to take it on a 100 mile or so drive, crank the tunes, or whatever, and go. Warm it up for a good half hour, pull over, check the level, and head home. As long as the light doesn't stay on, I wouldn't worry if it only flashes periodically, although I know it can be an annoyance. As vehicles age, some things (mostly emission related) cause the engine/trans light to be on all the time....
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!