The fuel gage selector switch is a momentarily-closed-type switch located on the vehicle dash. Contained within the fuel gage selector switch is a fuel indicator lamp (FIL). The fuel gage selector switch allows the operator to check the fuel level of either fuel tank-regardless of which fuel system is operating. The Alternative Fuels Engine Control Module (AF ECM) monitors the state of the fuel gage select switch input circuit. When the fuel gage selector switch is depressed the AF ECM responds by operating the fuel gage relay. Operation of the fuel gage relay determines which fuel tank level signal is received by the Powertrain Control Module (PCM). The PCM will send the fuel level information to the instrument panel fuel gage using the Class 2 serial data circuit. The fuel gage will display the NON-OPERATING fuel system's fuel level for about ten seconds after the fuel gage selector switch has been depressed. The PCM filters the fuel level display during vehicle movement, depress the fuel gage select switch 30 seconds after the vehicle speed sensor indicates the vehicle is at rest in order to avoid inaccurate gage displays.

The fuel indicator lamp (FIL) is contained within the fuel gage selector switch button. The fuel indicator lamp indicates which fuel system is in operation. The AF ECM controls the operation of the fuel indicator lamp. The fuel indicator lamp illuminates ONLY when the engine is operating on gasoline. The fuel indicator lamp will also illuminate for several seconds during start-up as a bulb check.