Fuel Gage Operation

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The CNG fuel level is determined by the PCM. The PCM monitors the FTP and FTT sensors that are located on the CNG tank high pressure lock-off solenoids. The PCM performs a calculation of the CNG pressure and CNG temperature in order to determine an accurate CNG fuel level. The gasoline fuel level is determined by the PCM in a conventional manner using an in-tank variable resistor sensor. Under normal conditions the instrument panel fuel gage displays the level of fuel that the vehicle is operating on. A fuel gage selector switch allows the two different fuel system tank levels to be displayed by the one instrument panel fuel gage. The fuel gage selector switch is a momentary-closed type switch located to the right of the instrument panel. The fuel gage switch allows the vehicle operator to observe the fuel level of the non-operating fuel system. The PCM monitors the status of the switch. When the switch is pressed, the PCM changes the fuel level signal to display the non-operating system fuel level. Once requested, the non-operating fuel system level will be displayed for about 10 seconds. The PCM communicates fuel level to the instrument panel fuel gage through serial data.