Might be for the optional handlebar switch. What is wrong with your trip function. I think I remember you saying you couldnt`t get the trip function to work. What happens when you push the o button? It should scroll through the different functions that you have activated ex clock, hr, trip, odo etc. To set a function to be displayed you have to hold the o button down while you are on the hour display. The active functions should then be displayed now use the + and - to activate and deactivate functions. then press and hold the o button to save the settings. Sorry if I am telling you something you already know.