Component Functional Description - Fuel Level Sensors Circuits

The Primary and Secondary Fuel Level Sensor Signals (saddle tanks or dual tanks)  are hard-wired to the Body Control Module (BCM). Both Fuel Level Sensor signals are a constant 12.0 volts. On a normally functioning system,  the raw signal voltage will read between approximately 0.5 volts (full stop) and 4.5 volts (empty stop). When there is an open in the circuitry the signal circuit voltage be 12.0 volts. The data reading value on the scan tool is clipped to read 5.0 volts when the signal circuit is open.  The BCM reads the voltage and converts the analog signals to digital signals. The digital signals are broadcast over the CAN bus. The Powertrain Control Module (PCM) receives and interprets the digital signals as a voltage read. The PCM, and in most cases the BCM, perform circuit fault diagnostics on the signal input.

The Fuel Level Rationality diagnostics are only performed by the PCM.  The Fuel Level rationality diagnostics are explained in more detail in the Fuel Level Rationality diagnostic information below.