From what you are stating, I will presume that this particular FG20-14 has an Operator's Presence Sensor (seat switch).
Here's what you are actually looking at.
The "10 flashes" of MIL means that the engine ECU has no fault codes stored (that would actually be 10 flashes repeated 4 times, which represents "4 zeroes").
The "3 flash" code you are seeing is being generated from the KOPS controller indicating a fault in the Komatsu Operator's Presence Sensor system.
A 3 flash code can mean a few things but I have found from experience that this is most often caused by a "burned out" Neutral indicator bulb. Because the KOPS system shares the engine MIL for its notification of a defect it can sometimes be confusing as to just what is going on.
First thing you need to do in this code is to confirm whether or not the Neutral indicator bulb on the monitor panel lights up when the transmission is in Neutral.
The KOPS controller does a "self check" of all circuits whenever the ignition is turned on and an open circuit on the Neutral light bulb is considered a defective condition by the KOPS controller.
The thing to remember on these "dual purpose MIL" set ups is that to display stored codes from the engine ECU, you must use the pedal tap dance (or the diagnostic reader tool) to request the data to be given via MIL.
The KOPS system, in contrast, automatically displays its flashing codes when the ignition is turned on.
And if that is not enough to cause confusion, consider that the MIL will light up and stay lit continuously if certain codes are registered by the engine ECU.
And if the engine ECU has the MIL lit, any codes being given out by the KOPS controller are not obvious, because while the KOPS controller is giving out its own notification signal, the MIL is already lit continuously and the KOPS codes are invisible, until you resolve the issue with the engine ECU codes.