Now your cookin' using the right instrument for the job. Duty Cycle scale is usually some odd set up on the meter and the manual is usually necessary to figure it out.
Since the duty cycle is staying solid, this is most likely a trouble code. This being solid at near 20% duty cycle indicates a problem with the Full Load Contact circuit. This is the throttle valve switch.
I would start by disconnecting the cable to the throttle valve switch and put your ohmmeter probes across the switch. Move the throttle from closed to wide open throttle and make sure the switch makes and breaks. If it does not, correct it by adjustment or switch replacement whichever is necessary. If it does work, you will need to trace the wiring to look for an open circuit along the way.
Hope this helps,