Circuit Description

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The fuel level sender changes resistance based on the fuel level. The ECM monitors the signal circuit of the fuel level sender in order to determine fuel level. When the fuel tank is full, the sender resistance is high and the ECM senses a high signal voltage. When the fuel tank is empty, the sender resistance is low and the ECM senses a low signal voltage. The ECM uses the signal circuit of the fuel level sender in order to calculate the total remaining fuel percent in the tank. The ECM (L81) sends the fuel level message via the CAN serial data circuit to the BCM or the ECM (L61) sends the fuel level message via the class 2 serial data circuit to the BCM. The BCM sends the fuel level percent to the IPC via the class 2 data circuit to display on the fuel gage. The fuel level information is also used for misfire and EVAP diagnostics.

This diagnostic tests for a lower than normal fuel level sender signal.