Fuel Gauge Operation

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

The CNG fuel level is determined by the Powertrain Control Module (PCM). The PCM monitors the Fuel Tank Pressure (FTP) and Fuel Tank Temperature (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 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 gauge displays the level of fuel that the vehicle is operating on. A fuel gauge selector switch allows the 2 different fuel system tank levels to be displayed by the one instrument panel fuel gauge. The fuel gauge selector switch is a momentary-closed type switch located in the headlight dimmer switch assembly. The fuel gauge 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 depressed 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 gauge through serial data.