P0750 Shift Solenoid A malfunction

[AKTaco]

Can anyone explain this error code? 02 Tacoma, A/T, V6, TRD, 39K miles.

Tried to post this twice so far, with no luck on getting the message to go through, so I'll send the short version this time and add details as we go.

Thanks in advance!

[AKTaco]

Ok, that one seemed to go through okay, so here are some more details...

HEAVY city/stop-n-go, short trip usage. Spends most of it's time in 4H due to icy, snowy roads. LOTS of idling time... 5-10 minutes at a time, 15-20 times a day, on the road running around the city anywhere from 8-15 hours a day, about 3,000 miles a month.

Check engine light came on after truck had been running/driving for about 2.5 hours, OBDII code says solenoid malfunction. I gradually accelerated from a complete stop on ice/snow, no slippage, but tach had a minor spike from 2200-2500 RPM, immediately after which, the light came on.

[AKTaco]

Part 3:

Dealer just performed 30K service at 36.5K miles about three weeks ago. Any connection, or just coincidence? He handed me an $800 estimate to repair, and of course, not covered under the tranny warrantee since it's an electronic component and bumper-to-bumper ran out at 36K. Told me they need the truck for a day to pull the pan and test the solenoids and harness individually to determine which one is bad, then another day to R & R once the new one comes in. Wouldn't the "A" tell them it's the #1 solenoid? Also told me it's fine to drive in the meantime... if it's fine to drive, then why does it need to be replaced? It's not like the solenoid will gradually get worse... if it's electronic, then it either works or it doesn't, right?