why does our printer pull from tray 2 when tray 4 is empty? Can we set it so it does not happen?

[meyerc]

why does our printer pull from tray 2 when tray 4 is empty? Can we set it so it does not happen?

[dansdaduk]

>> ... why does our printer pull from tray 2 when tray 4 is empty?

Probably because:

• Both trays contain the same paper size (e.g. A4 or Letter), which should be detected automatically by sensors attached to the paper width and length guides in the trays.
• Both trays contain the same paper type (e.g. Plain or Letterhead), as configured via front panel menus, or the Embedded Web Server equivalent.
• The print job(s) specify the particular paper size and type which matches both of the trays; with most modern Laserjet printers, the printer will print from the highest numbered matching tray first, if two or more trays match the print job criteria. 

>> ... Can we set it so it does not happen?

If the paper types are indeed different  (otherwise why would you be concerned?), configure the printer to set the appropriate paper type for each tray, from the 'limited value set' of available types supported by the device.

You'll then need to ensure that each of your print jobs specifies the appropriate paper size and type values, via the Print preferences dialogue.