Sending Unit And Sensor, Fuel Level: Operation: Operation
FWD
Front wheel drive (FWD) vehicles have a single fuel level sensor located on the fuel pump module.
As the fuel level float is moved the resistance changes in consistent incremental steps from low resistance (float up) to high resistance (float low).
The Body Control Module (BCM) provides a signal to the fuel level sensor. The BCM monitors the fuel level sensor for a specific change based on a calculated value and the vehicle operating conditions.
The fuel level sensor is only serviceable on the flex fuel vehicle (FFV).
AWD
All wheel drive (AWD) vehicles with saddle fuel tank configurations have primary (1) and secondary (2) fuel level sending units.
As the fuel level floats are moved the resistance changes in consistent incremental steps from low resistance (float up) to high resistance (float low).
The Body Control Module (BCM) provides a signal to the fuel level sensor. The BCM monitors the fuel level sensor for a specific change based on a calculated value and the vehicle operating conditions.
The fuel pump module is constantly transferring fuel from the secondary side to the primary side of the fuel tank. Because the siphon tube flow rate exceeds the vehicle fuel consumption rate, the secondary side of the tank will be emptied before the primary side. When the fuel tank is full and the fuel level is equal on both sides, the BCM averages the input from both sending units and sends one signal to the instrument cluster for fuel gauge position. When the fuel level becomes low enough so that equalizing of the fuel level from sloshing is no longer possible, the pump continues to transfer fuel from the secondary side to the primary side. When the secondary side is nearly empty, the BCM ignores the input from the secondary side and only displays the input value from the primary side.
The main fuel level sensor located on the fuel pump module (1) is not serviceable on AWD vehicles. The secondary fuel level sensor (2) on AWD vehicles is serviceable.