To pull the codes, shut the tractor down and then turn the key to the run position, press and hold the switch that toggles the display for a couple seconds, it will then show you the error codes that is stored.
OP has a 2009 5085M no fancy scroll mode yet FIY.
Also, Orig. Poster where are you getting your diesel from?
Bulk, Gas Station
Stored in? Bulk tank, 5 Gallon Tanks, etc etc.
If you got a bulk tank, change the filter on it if it has one.