ENUS6937Affected Products:
Color multifunction: CX82x, CX860, XC6152, XC6153, XC8155, XC8160, XC8163, MB2770
Monochrome multifunction: MX72x, MX82x, XM53xx, XM73xx

Issue Description
A blue screen with a "Firmware Error [900.00]" message appears on the printer display during a scanner operation; either when the scanner calibrates upon power up or when making scans or copies.

Solution

Update Firmware. With Firmware EC7 or greater, the correct scanner error code will be posted by the printer, instead of the 900.00 Firmware Error.

Verify whether the issue is with the automatic document feeder (ADF) or flatbed scanner.
If the error appears only when copying or scanning a document, it is most likely to be an ADF scanner issue.
If the error occurs upon powering the printer on, it is more likely a flatbed scanner issue.

Disable ADF scanner.
Access the printer configuration menu
Navigate to Settings > Device > Maintenance > Configuration menu
Select Scanner Configuration > Disable Scanner > ADF disabled

Then perform a flatbed copy or scan.
If the error persists then it is a flatbed issue.
If the error doesn’t reoccur, then it is an ADF issue.

Still Need Help?
Have the following available when calling Lexmark Technical Support;
Printer model(s)
Printer serial number (xref_HO3996_xref)
LEGACY ID: SO8804