Fuel Gage Inaccurate or Inoperative (Single Tank)
Fuel Gauge Inaccurate or Inoperative
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
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 gauge.
Diagnostic Aids
A partially filled fuel tank and filling the fuel tank with the ignition ON or engine RUNNING may cause an inaccurate or erratic fuel gauge. This condition may cause a fuel system DTC to set and the fuel gauge to default to empty. Refer to Fuel Gauge Description and Operation (Description and Operation).
Reference Information
Schematic Reference
Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Fuel Gauge Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Special Tools
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
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 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 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.
3. Ignition OFF, test for less than 1 ohm of resistance 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 A to the secondary fuel level sensor signal circuit terminal A. Install a Signal Generator and Instrument Panel Tester between the jumped signal circuits and ground.
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 terminal A 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 gauge displays a range that varies between empty and full as the signal generator resistance changes.
• If the fuel gauge is incorrect, replace the instrument panel cluster (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, remove the 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 of resistance between signal terminal A and the low reference terminal D.
• 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.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Primary Fuel Level Sensor Replacement (Service and Repair) for the 4.6L engine
* Primary Fuel Level Sensor Replacement (Service and Repair) for the 4.4L engine
* Primary Fuel Level Sensor Replacement (Service and Repair) for the 3.6L engine
* Secondary Fuel Tank Module Replacement (Secondary Fuel Tank Module Replacement) for the 4.6L engine
* Secondary Fuel Tank Module Replacement (Secondary Fuel Tank Module Replacement) for the 4.4L engine
* Secondary Fuel Tank Module Replacement (Secondary Fuel Tank Module Replacement) for the 3.6L engine
* Control Module References (Programming and Relearning) for the ECM or IPC replacement, setup, and programming