Fuel Gauge Malfunction
Fuel Gauge Malfunction
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 gauge.
Reference Information
Schematic Reference
Instrument Cluster Schematics Instrument Cluster Schematics
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
Description and Operation
Instrument Cluster Description and Operation Instrument Cluster
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
Control Module References Control Module References 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 ohms 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 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 circuit test normal, replace the ECM.
5. Vary the signal generator resistance between 40 and 250 ohms. Verify that the fuel gauge displays a range that varies between empty and full as the signal generator resistance changes.
• If the fuel gauge is incorrect, replace the fuel gauge.
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 ohms and greater than 119 ohms 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 Fuel Level Sensor Replacement for the 3.9L engine
* Control Module References Control Module References for the ECM replacement, setup, and programming