With the engine running press and hold the button on the left of the display for at least 8 seconds. If you have a cruiser model press and hold both buttons on the left side of the display for 8 seconds. This will give you a 2 digit error code on the display.
Also you need to note which warning light showing (overheat, check engine, or oil pressure, low fuel).
2008 Yamaha FX HO Cruiser
2010 Hurricane Sundeck 2100