Circuit Description

The CNG fuel gauge system consists of the Fuel Tank Pressure (FTP) sensor, Fuel Tank Temperature (FTT) sensor, Pulse Width Modulated (PWM) output circuit, dash mounted fuel gauge and dash mounted fuel gauge select switch (Bi-fuel/KL6 only). Alternative Fuels Engine Control Module (AF ECM) monitors fuel pressure and fuel temperature in CNG fuel tank. Volume of CNG varies with pressure and temperature. In order to display an accurate fuel gauge reading, AF ECM will perform a calculation based upon fuel pressure and temperature and determine correct amount of fuel remaining in fuel tank. AF ECM converts calculated fuel level into a PWM signal that is monitored by PCM. PCM sends fuel level information to instrument panel fuel gauge via Class 2 serial data circuit. Vehicles that are equipped with Bi-fuel (KL6) option also utilize a fuel gauge select switch. Fuel gauge select switch is monitored by PCM. When switch is pressed, PCM will display fuel level for non-operating fuel system, for about 10 seconds.