Theory Of Operation

The Body Control Module (BCM) helps determine the amount of fuel remaining in the Fuel Tank by monitoring the Fuel Level Sensor and sending CAN Bus fuel level messages to the modules that require fuel level information. The BCM monitors the Fuel Level Sensor through hardwired Fuel Level Sensor Signal and Fuel Level Sense Return circuits. The Fuel Level Sensor includes a Fuel Level Sensor Arm and Float, along with an integral variable resistor, which operates between 51.0 Ohms and 992.0 Ohms. The resistance value of the Fuel Level Sensor varies, depending on the amount of fuel remaining in the Fuel Tank. When the Fuel Level Sensor Arm and Float is at the highest point of travel (Fuel Tank FULL), the resistance is approximately 51.0 Ohms. When the Fuel Level Sensor Arm and Float is at the lowest point of travel (Fuel Tank EMPTY), the resistance is approximately 992.0 Ohms.

On a normally functioning system,  with no circuit faults and the harness connectors plugged in, the voltage on the Fuel Level Sensor Signal circuit, at the Fuel Level Sensor, should be between approximately 1.0 volt (Fuel Tank FULL) and 10.5 volts (Fuel Tank EMPTY). The voltage is used up through the resistor within the Fuel Level Sensor, therefore the voltage on the Fuel Level Sense Return circuit should be zero volts.

The voltage reading in the scan tool is scaled to read between approximately 0.6 volts (Fuel Tank FULL) and 4.5 volts (Fuel Tank EMPTY).