The fuel level sender changes resistance based on the fuel level. The engine control module (ECM)/powertrain control module (PCM) 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/PCM senses a low signal voltage. When the fuel tank is empty, the sender resistance is high and the ECM/PCM senses a high signal voltage. The ECM/PCM uses the signal circuit of the fuel level sender in order to calculate the total remaining fuel percent in the tank. The ECM/PCM sends the fuel level message via the CAN serial data circuit to the body control module (BCM). The BCM sends the fuel level percent to the instrument panel cluster (IPC) via the class 2 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

Description and Operation

Electrical Information Reference

Scan Tool Reference

1. Ignition OFF, disconnect the harness connectors at the fuel level sensor.
2. Ignition OFF, test for less than 1 ohm of resistance between terminal C of the primary fuel level sensor and terminal B of the secondary fuel level sensor.

⇒	If greater than 1 ohm, test the circuit between terminal C of the primary fuel level sensor and terminal B of the secondary fuel level sensor for an open/high resistance.

3. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM/PCM.

4. Install a Signal Generator and Instrument Panel Tester between the signal circuit terminal and ground.
5. Ignition ON, vary the signal generator resistance between 40 and 250 ohms. Verify that the scan tool Fuel Level parameter displays a range that varies between 1 and 55 liters (0.26 and 14.5 gallons) as the signal generator resistance changes.

⇒	If not displaying the specified range, test the signal circuit for an open/high resistance. If the circuits test normal, replace the ECM/PCM.

6. Vary the signal generator resistance between 40 and 250 ohms. Verify that the fuel gage displays a range that varies between empty and full as the signal generator resistance changes.

⇒	If not displaying the specified range, replace the IPC.

7. If all circuits test normal, test or replace the appropriate fuel level sensor.

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.