Kohler 30RYG generator with G220 transfer switch... weekly exerciser stopped running and won't run manually?

Emergency shutdown operation is required when one of the above conditions occurs in diesel generator set.Diesel generating set itself has an emergency stop button, at this time, press the emergency stop button or quickly press the stop control handle of fuel injection pump to the stop position, the diesel generator will quickly cut off the load, and immediately close the throttle, while the red "emergency stop" light is on. Need to press the button again to delete the emergency stop signal. If there are serious faults or distribution faults, you can also press the button on the control panel, and the unit will stop immediately.

In fact, all faults always give operators some warning signal before spare parts break down or engine damage occurs. So the operators need to be smart, and notice alarm signals (sudden drop in oil pressure, abnormal sound, etc.) and immediately stopping the engine.
Emergency shutdown operation is different from normal shutdown operation.
Emergency shutdown operation.Once the operator finds that there is a serious fault or distribution fault in thediesel generating set, he can press the emergency stop button of the control panel to stop the unit immediately. If there is no special circumstances, we advise users not to stop the unit at will through the emergency stop button.

It is most likely set to exercise once a week and run for about 1/2 hour or so

Is it possible that some other timer is kicking in on Friday? Something not related to the ATC-300?

Did it always do this? Is there a factory 'exercise' (non-load) built into the transfer assembly?

Try disconencting the remote start wires between the transfer switch and the generator, if ot still does it you have a bad control board. If it stops, then check the transfer switch for correct wiring of utility and generator power wires, also check with an ohm meter if the run contacts in the transfer switch are closed, that would indicate loss of sensing, or bad board

On exercise it isn't under load, you may have too much gas pressure, have the gas pressure and fuel/air ratio checked on the mixer

Product manual does not have troubleshoot section.
The operation might be normal, and within expected parameters, or it might have a glitch.
Suggest you contact Kohler Power directly:
http://kohlerpower.com/contactus/contactus.htm?sectionNumber=

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Although A bit inconvienent this does seem to be the norm for some Kohler units. Actually a small price to pay rather than having a technician come out to replace the ATS control board. There are time delays that could be set longer to keep the unit running longer and may prevent this from happenng

http://www.homegeneratorsystems.com/service_support/manuals/index.cfm?rd=1

This link will take you to their site where you can download their manual.

Setting Exercise Timer
The Home Standby Generator is equipped with an exercise
timer that will start and exercise the system once every
seven days. During this exercise period, the unit runs for
approximately 20 minutes and then shuts down. Electrical
load transfer DOES NOT occur during the exercise cycle
(unless an utility power outage occurs).
A switch on the control panel is labeled “Set Exercise”
(depicted on page 10).The specific day and the specific time
of day this switch is pressed is programmed into the
control board memory.This date and time is then used to
automatically initiate the system exercise cycle.
To perform the Set Exercise procedure:
1. Choose the day and time you want your Home
Standby Generator to exercise.
2. On that day and time, set the AUTO/OFF/MANUAL
switch to OFF.
3. Press and hold down the “Set Exercise” switch for two
seconds.
4. Set the AUTO/OFF/MANUAL switch to AUTO.“Set
Exercise” is complete.
For example, if you press the “Set Exercise” switch on
Sunday morning at 10:00 AM, the unit will run an exercise
cycle the following Sunday at 10:00 AM (+/- 1/2 hour).
NOTE: “Set Exercise” will only work if the unit is in the
Automatic mode and this exact procedure is followed.The
exerciser does not need to be re-set if the 15 Amp fuse is
removed or changed.The exerciser will need to be re-set if
the 12 Volt DC battery is disconnected.
If you want to change the day and time the unit exercises,
simply perform the “Set Exercise” procedure at the exact
weekday and time you want it to take place.
• To prevent possible injury that might be caused by such sudden
starts, always set the AUTO/OFF/MANUAL switch to OFF.
• Remove the 15 Amp fuse before working on or around the
generator or transfer switch.

On your Automatic Transfer Switch ( the little gray box you see on the right in the picture above) you have two blue buttons. One is a Manual test switch. The other has a clock on it and this is your exercise set button. Hold it down for a FULL 3 seconds if you want it to excercise without a load (not powering your home) Hold it down for a FULL 6 seconds if you want it to exercise with a load every week. Your generator will start and run for 20 minutes, and then shut down. Now every week your generator will exercise at the time and day that you pushed the set button.