What model Kohler genset do you have? If you don't know, can you take and post a picture of either the model tag or of the controller box on it?
For most generators, it is sufficient to turn them off for 30 seconds or more via either their off switch or the battery switch. Since you replaced the battery, I'm guessing yours isn't one of those.
For others, they are cleared via the controller. It is usually via a sequence such as using the general-purpose key on the control to acknowledging the existence of fault messages, then walking through the list of fault messages (in this case one of them) on at a time, clicking the same button to acknowledge the fault message, and then using a cursor key to choose YES or NO to Confirm/Clear, and then the general-purpose key to confirm that action and go on to the next one in the fault list or return to a top-level overview/status screen.