Pioneer AVH-X5500BHS Owner's Manual page 74

The PEH software update process will automatically begin and the update progress is displayed
on screen:
15. Wait until the update process is complete. Once the firmware update process is complete, the
unit will display the following screen:
16. Remove the USB storage device from the USB/iPod input port.
17. Press the reset button with a pen tip or other pointed instrument.
18. The firmware update is now complete.