Its a Trans Pressure Switch Malfunction code if you're referring to OBD 2 code P1810.

Change filter and fluid and check for extra metal or clutch stuff in the bottom of pan.

Clear code and see what the transmission does.

The code is for a pressure switch problem but many things can trip the code.
Speed sensors readings and bad wiring or lose connection or ground or 12 volt power lose to switch.
To check the code out.
You would need a engine/transmission scanner and a good volt/ohm meter to check out the wiring and switch and sensors.

Crusty stuff in dip stick tube is condensation and rust.
You need to lubercate your dip stick. :grinyes:
Just clean it as best as you can and smear a little greese on the dip stick and tube area.
Make sure a ac line or water leak is not above dip stick area.