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

Schematic Reference

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

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 of resistance 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 of resistance between the secondary 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.

4. Jumper the primary fuel level sensor signal circuit terminal 1 to the secondary fuel level sensor signal circuit terminal 1. Install a Signal Generator and Instrument Panel Tester between the jumped signal circuits and the low reference circuit terminal 4.
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 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, disconnect the harness connector at the primary and secondary fuel level sensors.
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 of resistance 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 of resistance between signal terminal 1 and the low reference terminal 4.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.