I found the standard Nagios check_hpjd plugin to be unreliable at times - so I wrote my own which checks toner levels via snmp.
The file "check_toner_c.sh" checks the toner levels on all HP / UTAX / Kyocera Printers. The other file is for the Black and White Utax / Kyocera Models only. If you have a color Utax / Kyocera Printer, Use the color plugin to check their Black Ink Levels.
You Need snmpget for this plugin to work, this is generally part of snmptools.
Command syntax is: check_toner_c.sh , eg: check_toner_c.sh 192.168.0.2 K
Valid Options for Toner color are:
C (for Cyan) M (for Magenta) Y (for Yellow) K (for Black)
Note that these are case sensitive!!