Circuit Description

The primary fuel level sender and the secondary fuel level sender change resistance in response to fuel level. The ECM monitors the signal circuit of the primary fuel level sender and the secondary fuel level sender in order to determine the fuel level. When the fuel tanks are full, the resistances of both fuel level senders are high, and the ECM senses a high signal voltage on both the signal circuit of the primary fuel level sender and the signal circuit of the secondary fuel level sender. When the fuel tanks are empty, the resistances of the fuel level senders are low, and the ECM senses a low signal voltage. The ECM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of remaining fuel in the tanks. The ECM sends the fuel level percentage via the class 2 serial data circuit to the instrument cluster in order to control the fuel gage. The fuel level information is also used for misfire and EVAP diagnostics. This diagnostic tests for a lower than normal primary fuel level sender signal.