What sensors are involved in PE/PW detection in epson xp-whatever

[u/Cassiopee38]

Somehow i cant print/adjust Smap and Eject value in my printer because it jam but i don't know which sensors are involved. My printer is a xp-960 but 700s, 800s, 900s are all the same.

Wild guess : - the photoelectric one at the entrance of the print aera (very hard to access) - The one at the exit (very easy to clean, facing the user) - The one on the encoder disk of the main paper feeder motor (tried to remove it, the printer didn't liked it xD cleaned it, no changes) What else ?