The transmission fault codes that a technician reads on his diagnostic scanner tell him the area or system of the transmission the computer has recognized with a problem. To read the code and replace a part would never be the correct procedure to follow.
The code could be for an electronic sensor that has a broken wire or a loose connection. The technician must follow the factory diagnostic chart to determine the exact cause of the fault. Just replacing a part would be the same as guessing rather than knowing what is causing the problem.
This is the reason DIY or “do it yourself” auto repair can cost the owner more to replace parts rather than having a technician diagnose the problem correctly.