Nikon D6 Reference Manual page 1066

Alert
Top
control Viewfinder
panel
—
A
(flashes)
%
(flashes)
1
(flashes)
—
1014 Alerts and Error Messages
F H
Camera unable to focus using autofocus.
(flashes) Change composition or focus manually.
A (Bulb) selected in mode S.
A
•
Change shutter speed.
(flashes)
•
Select mode M.
% (Time) selected in mode S.
%
•
Change shutter speed.
(flashes)
•
Select mode M.
k
Processing in progress.
(flashes) Wait for processing to complete.
Flash has fired at full power.
N Photo may be underexposed. Check distance to
(flashes) subject and settings such as aperture, flash
range, and ISO sensitivity.
Problem/solution