The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via the serial data circuit to the body control module (BCM). The BCM then sends the fuel information to the instrument panel cluster (IPC) via the serial data circuit in order to display the fuel gage.

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Instrument Cluster Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, verify DTC P0461, P0462, P0463, or P0464 is not set.

1. Ignition OFF, disconnect the harness connector at the fuel level sensor.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal listed below and ground.

•	Low Reference Terminal B (5.3L)

•	Low Reference Terminal C (4.3L, 4.8L or 6.0L)

•	Low Reference Terminal C (6.6L Diesel)

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

3. Install a Signal Generator and Instrument Panel Tester between the signal circuit terminal and the low reference circuit terminal listed below:

•	Signal Terminal C (5.3L)

•	Low Reference Terminal B (5.3L)

•	Signal terminal B (4.3L, 4.8L or 6.0L)

•	Low Reference Terminal C (4.3L, 4.8L or 6.0L)

•	Signal Terminal B (6.6L Diesel)

•	Low Reference Terminal C (6.6L Diesel)

4. Ignition ON, vary the signal generator resistance between 40-250 ohms. Verify that the scan tool Fuel Tank Level Remaining parameter displays a range that varies between 5 and 95 percent as the signal generator resistance changes.

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

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

⇒	If the gage is incorrect, replace the IPC.

6. If all circuits test normal, perform the fuel level sensor component test before replacing the fuel level sensor.

1. Ignition OFF, disconnect the harness connectors at the fuel level sensor.
2. While sweeping the fuel level sensor through its full range of motion, test for a minimum value less than 41 ohms and a maximum value greater than 119 ohms of resistance between the signal terminal and the low reference terminal listed below:

•	Signal Terminal C (5.3L)

•	Low Reference Terminal B (5.3L)

•	Signal terminal B (4.3L, 4.8L or 6.0L)

•	Low Reference Terminal C (4.3L, 4.8L or 6.0L)

•	Signal Terminal B (6.6L Diesel)

•	Low Reference Terminal C (6.6L Diesel)

⇒	If not within the specified range, replace the fuel level sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.