My L2 is not working but sometimes it does

Can you give more details to your problem?
Like if its not detecting, not pressing in?

If its not being detected you will have to tear it apart How to not break the outer shell while opening the DualShock 4 CUH-ZTC1 Generation 2 you can follow this guide to open it the L2 triggers will be on a plastic soft surface you can get a q tip and clean the plastic button like surface and make sure thats it doesnt move anywhere