Fuel Level Sending Unit Sensor: Operation

For fuel gauge operation:  As fuel level increases, the float and arm move up. This increases the sending unit resistance, causing the fuel gauge to read full. As fuel level decreases, the float and arm move down. This decreases the sending unit resistance causing the fuel gauge to read empty.

After this fuel level signal is sent to the instrument cluster, the instrument cluster will transmit the data across the J1850 bus circuits to the PCM.

For OBD II emission requirements:  The voltage signal is sent to the instrument cluster to indicate fuel level. The cluster transmits the fuel level to the PCM where it is used to prevent a false setting of misfire and fuel system monitor trouble codes. This occurs if the fuel level in the tank is less than approximately 15 percent of its rated capacity.