The primary fuel level sender and the secondary fuel level sender changes resistance based on fuel level. The engine control module (ECM) monitors the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to determine the fuel level. When the fuel tank is full, the resistances of both fuel level senders are low and the ECM senses a low signal voltage on both the signal circuits of the primary fuel level sender and the secondary fuel level sender. When the fuel tanks are empty, the resistances of the fuel level senders are high and the ECM senses a high 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 tank. The ECM sends the fuel level percentage via serial data circuit to the instrument cluster in order to control the fuel gage.

A partially filled fuel tank and filling the fuel tank with the ignition ON or engine RUNNING may cause an inaccurate or erratic fuel gage. This condition may cause a fuel system DTC to set and the fuel gage to default to empty. Refer to Fuel Gage Description and Operation.

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel Gage Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 33431-C Instrument Panel Tester

Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4-98 percent.

1. Ignition OFF, disconnect the harness connector at the primary and secondary fuel level sensors.
2. Ignition OFF, test for less than 1 ohm between the primary fuel level sensor low reference circuit terminal 4 and ground.

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

3. Ignition OFF, test for less than 1 ohm between the secondary fuel level sensor low reference circuit terminal D and ground.

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

4. Jumper the primary fuel level sensor signal circuit terminal 1 to the secondary fuel level sensor signal circuit terminal A. Install a Signal Generator and Instrument Panel Tester between the jumped signal circuits and and the low reference circuit.
5. Ignition ON, vary the signal generator resistance between 40 and 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 displaying the specified range, test both signal circuits for an open/high resistance. If the circuits test normal, replace the ECM.

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 the fuel gage is incorrect, replace the IPC.

7. If all circuits test normal, perform the fuel level sensor component test before replacing either the primary or secondary fuel level sensor.

1. Ignition OFF, remove primary and secondary fuel level senders.
2. While sweeping the primary 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 between signal terminal 1 and the low reference terminal 4.

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

3. While sweeping the secondary 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 between signal terminal A and the low reference terminal D.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.