Accu-Chek Nano Owner's Booklet page 88

The batteries are almost out of
power. Change the batteries now. If
the message reappears after the
batteries have been replaced, reset
the meter. To reset the meter, slide
the battery drawer out of the meter,
press any meter button, then reinsert
the battery drawer back into
position.
86
nOTE
If you see any other error display, contact the ACCU‑CHEK Customer Care Service Center at
1‑800‑858‑8072.
The time and date settings may be
incorrect. Make sure the time and
date are correct and adjust, if
necessary.