"E9" in the display means the batteries are almost out of power. Change the batteries now. If the message reappears after the batteries have been replaced, remove the batteries again, press and hold the power/set button for at least 2 seconds, wait 20 seconds, and then reinsert the batteries.

Accu-Chek Guide Me

Accu-Chek Guide

Accu-Chek Nano

Accu-Chek Aviva Meter