Make sure that [Auto Paper Select] is selected.
Place the originals, and then press the [Start] key.
Only the trays that satisfy all the following conditions can be selected in Auto Paper Select mode. Trays with a lock mark () will not be automatically selected. For details, see "Changing Tray Paper Settings", Paper Settings.
[Plain Paper] or [Recycled Paper] is selected in [Paper Type] under [Tray Paper Settings]
[Paper Weight 2] (66.0–80.9 g/m2) or [Paper Weight 3] (81.0–100.9 g/m2) is selected in [Paper Weight] under [Tray Paper Settings]
[Yes] is selected in [Apply Auto Paper Select] under [Tray Paper Settings]