Legacy 97 with automatic transmission problems.

Hello everyone a few months ago I enrolled in MDM and today I played the need to ask for help since a friend has a legacy 97 with automatic transmission problems, when one turns on the engine the Power light flashes several times, we enter with a scanner to the ECU and yields the following failures 15 and 21 one refers to the ATF temperature sensor and the other to a solenoid that can have problems, this legacy is fwd. An eg 2.0 Can anyone guide me how do I repair this? Could you access through the transmission crankcase? Or I will have to disassemble the entire unit, the errors are not erased kuek !!!