Epson Stylus Pro 7900 - Checking Error Messages and Lights

Pro 7900 and 9900 Field Repair Guide 10/6/10
Sensor (Platen Gap) Removal Printer Component, Software Item, LCD Display, Printer Button Page 186.
6. Turn the Platen Gap Gear until the Home Position Window is aligned with the Sensor.
Turn this Gear until the Sensor is in the Window.
Sensor in the Window.