Fuel Gage Inaccurate or Inoperative (Single Tank)

Fuel Gauge Inaccurate or Inoperative

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

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 serial data circuit to the instrument cluster in order to control the fuel gage.

Reference Information
Schematic Reference

Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Instrument Cluster Description and Operation (Description and Operation)
* Fuel System Description (Fuel System Description) for the 3.5L engine
* Fuel System Description (Fuel System Description) for the 3.9L engine

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Programming and Relearning (Programming and Relearning) for scan tool information
Special Tools

J 33431-C Instrument Panel Tester

Circuit/System Testing

Note: If equipped, the following tests can be performed at an inline connector. See schematics for the corresponding terminals to test at.

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 C 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. Install a Signal Generator and Instrument Panel Tester between the signal circuit terminal B and the fuel level sensor low reference circuit terminal C.
4. Ignition ON, vary the signal generator resistance between 40 and 250 ohm. 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 circuit test normal, replace the ECM.

5. Vary the signal generator resistance between 40 and 250 ohm. 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 fuel gage.

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

Component Testing

1. Ignition OFF, remove the fuel level sender.
2. Sweep the sensor through the entire range while monitoring the resistance between the signal terminal B and the low reference terminal C. The resistance should vary between less than 45 ohm and greater than 119 ohm without any spikes or dropouts.

• If not within the specified range or is erratic, replace the fuel level sensor.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Fuel Level Sensor Replacement (Service and Repair) for the 3.5L engine
* Fuel Level Sensor Replacement (Service and Repair) for the 3.9L engine
* Programming and Relearning (Programming and Relearning) for the ECM or IPC replacement, setup, and programming