How to change error return for native SNMP primter sensor?

Yes, you can click the respective channel in the sensor, set the default Lookup to none, then select "Enable Limits" and define the new Lower Error and/or Lower Warning limits, for instance 1, any values below 1 will then trigger the respective alert.

For more details about channel settings, please refer to:

• PRTG Manual: Sensor Channels Settings

See also the Paessler website:

• How to set up limits in PRTG in 4 steps

Please beware that you may see values which may not make sense at first, for example -1 or -2 or -3, which are special values used by the MIB in specific conditions as described in the documentation of the MIB:

prtMarkerSuppliesLevel OBJECT-TYPE
    SYNTAX     Integer32
    MAX-ACCESS read-write
    STATUS     current
    DESCRIPTION
         "The current level if this supply is a container;
         remaining space if this supply is a receptacle. If this
         supply container/receptacle can reliably sense this
         value, the value is reported by the printer and is read-
         only; otherwise, the value may be written (by a Remote
         Control Panel or a Management Application). The value (-
         1) means other and specifically indicates that the sub-
         unit places no restrictions on this parameter. The value
         (-2) means unknown.  A value of (-3) means that the
         printer knows that there is some supply/remaining space,
         respectively."
    ::= { prtMarkerSuppliesEntry 9 }

Best Regards,
Luciano Lingnau [Paessler Support]