HP Deskjet 6122 Color Inkjet Printer - Manual (Page 60)

If Automatic is selected as the paper tray, verify that the upper tray contains
paper. If the upper tray is empty, the Automatic Paper-Type Sensor is not
operational for that print job.
turning off the automatic paper-type sensor
Open the Print dialog box and choose the following settings:
panel setting
General Source: Lower Tray
Paper Type/Quality
Paper Group: Any setting other than
Automatic
—or—
Quality: Draft
Mac OS X
turning on the automatic paper-type sensor
Open the Print dialog box and choose the following settings:
panel setting
Paper Type/Quality
Paper Type: Automatic
Quality: Best , Normal , or Fast
Normal
Source: Upper Tray or Automatic