The tachometer displays engine speed in rpm and is equipped with a Liquid Crystal Display (LCD) that will display actual engine hours or diagnostic information (SPN-FMI). Under normal operating conditions the LCD will display actual engine hours. When an engine event becomes active, the LCD will switch between the engine hours and the active SPN-FMI. The LED on the associated gauge will come on. Refer to the engine troubleshooting guide for SPM-FMI meanings.