My bad! I forgot to also mention that the Dash 14s that have the Komatsu Operator Presence Sensor system also feature a "Mast Locked Lamp" even if the truck DOES NOT have the hydraulics lockout featured in the configuration.
I know that the 2006 year models were only required to interrupt the transmission drive if seat is vacant, so the trucks built as 2006 models do not have the necessary locking solenoids for the mast functions installed, but they still have a "mast lock" bulb and if that bulb is burned out (or missing) it too will upset the KOPS controller when it does the bulb check at start up.
2007 year models were required to interrupt transmission drive AND mast functions if the seat is vacant.
So let me guess, the missing bulb was the one to the left of the engine MIL.