Fuel Gage Inaccurate or Inoperative
Fuel Gage Inaccurate or Inoperative
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
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.
Special Tools Required
J 33431-C Instrument Panel Tester
Circuit/System Verification
Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4-98 percent.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the fuel level sensors.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground.
^ If greater than the specified range, test the circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition OFF, test for less than 1 ohm between the fuel level sensor signal circuit terminal B and the fuel level sensor signal circuit terminal E.
^ If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
4. Ignition OFF, install a signal generator and instrument panel tester between the signal circuit terminal D and the low reference circuit terminal B.
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 the signal circuit for an open/high resistance. If the circuit 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.
Component Testing
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 between signal terminal D and the low reference terminal B.
^ 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 E and the low reference terminal B.
^ If not within the specified range, replace the secondary fuel level sensor.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Primary Fuel Level Sensor Replacement for the 3.4L engine
* Primary Fuel Level Sensor Replacement for the 3.6L engine
* Fuel Level Sensor Replacement - Secondary for the 3.4L engine
* Fuel Level Sensor Replacement - Secondary for the 3.6L engine