Circuit Description

The primary fuel level sender and the secondary fuel level sender change resistance in response to fuel level. The engine control module (ECM) or the powertrain control module (PCM) 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/PCM 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/PCM senses a low signal voltage. The ECM/PCM 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/PCM 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 stuck primary fuel level sensor signal. The ECM/PCM sets this DTC if the primary fuel level sensor signal appears to be stuck based on a lack of signal variation expected during normal operation.