Fuel Gage Inaccurate or Inoperative
Fuel Gage 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 fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM)/powertrain control module (PCM) 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/PCM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM/PCM senses a high signal voltage. The ECM/PCM uses the signal circuit of the fuel level sensor in order to calculate the percentage of fuel remaining in the tank. The ECM/PCM sends the fuel information to the instrument panel cluster via the serial data circuit in order to control the fuel gage and display the fuel level.
Reference Information
Schematic Reference
* Instrument Cluster Schematics (Instrument Cluster Schematics)
* Engine Controls Schematics (Electrical Diagrams)for the 2.8L, 3.0L, 3.2L and 3.6L engines
* Engine Controls Schematics (Electrical Diagrams) for the 3.8L engine
* Engine Controls Schematics (Electrical Diagrams)for the 4.8L, 5.3L, 6.0L, 6.2L and 7.0L engines
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 2.8L, 3.0L, 3.2L and 3.6L engines
* Fuel System Description (Fuel System Description)for the 3.8L engine
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
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the fuel level sensor.
2. Ignition OFF, test for less than 1 ohm of resistance between the fuel level sensor 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/PCM.
3. Install a Signal Generator and Instrument Panel Tester between the fuel level sensor 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 or Fuel Level 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/PCM.
5. 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.
6. If all circuits test normal, perform the fuel level sensor component test before replacing the fuel level sensor.
Component Testing
1. Ignition OFF, disconnect the harness connector at the fuel level sensor.
2. While sweeping the fuel level sensor through its full range of motion, test for a minimum value of less than 41 ohms and a maximum value greater than 119 ohms of resistance between signal terminal B and the low reference terminal C.
• If not within the specified range, 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 2.8L, 3.0L, 3.2L and 3.6L engines
* Fuel Level Sensor Replacement (Service and Repair)for the 3.8L engine
* Fuel Level Sensor Replacement (Service and Repair)for the 4.8L, 5.3L, 6.0L, 6.2L and 7.0L engines
* Control Module References (Programming and Relearning)for the ECM/PCM and IPC replacement, setup and programming