Next Maintenance Date

you cannot reset the alert.  The calibration must be performed by the OEM per the operator manual, although you can replace the O2 cell which is pn 4-072214-00 if that is what you are after!

Calibration requires specific test equipment which seem to not be available (obsolete?).  but it is best to have them do it.  I send all my test equipment to a certifier who sends this unit out to the OEM as well.

Not sure if that helps or gives you a direction, but I highly suggest you send it in for them to cal for you.