Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The fuel level sender changes resistance based on the fuel level. The engine control module (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 low and the ECM senses a low signal voltage. When the fuel tank is empty, the sender resistance is high and the ECM senses a high 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 sends the fuel level message via the serial data circuit to the body control module (BCM). The BCM sends the fuel level percent to the instrument panel cluster (IPC) via the serial data circuit to display on the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.

Schematic Reference

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

1. Ignition OFF, disconnect the harness connector at the fuel level sensors. Install a signal generator and instrument panel tester between the signal circuit and the low reference circuit.
2. Ignition ON, vary the resistance on the signal generator from 40 to 250 ohms. Verify that the scan tool Fuel Tank Level Remaining parameter displays the correct fuel level percent.

⇒	If the fuel level percent is incorrect, test the signal circuit and the low reference circuit for an open/high resistance. If the circuits test normal, replace the ECM.

3. Ignition ON, vary the resistance on the signal generator from 40 to 250 ohms and monitor the fuel gage.

⇒	If the gage is incorrect, replace the IPC.

4. If all circuits test normal, test or replace the fuel level sensors.

Measure the resistance of the float arm of the fuel level sender while moving the float arm between 40-250 ohms.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.