unknow code

Question

I went to a mechanic and they conected the computer to my chevrolet optra 2008 automatic, I remember the code said Solenoid 3 and 4, but I dont remember the code someone can help me to know whic is the code?

Answer 1

Solenoid 3 and 4,this would be P0783 This is a transmission code

Answer 2

Do i have to change I just the solenoid?  because the mechanic said I also have to change the 4 piston(diafragma ) is it necessary ? Inside the box I meant disarmy the changes box.

regards.