Fuel Gauge Inaccurate or Inoperative
Fuel Gauge Inaccurate or Inoperative (without LC8)
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 and the type of fuel in order to determine the fuel level. For regular unleaded fuel the ECM monitors a constant signal. When the vehicle has approximately 20% or greater ethanol for E85 applications, the ECM controls a pulse cycle signal where it monitors the signal and calculates the fuel level percentage only during the on pulse of approximately 100 ms.
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 the 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 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
Instrument Cluster Description and Operation Description and Operation
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 Verification
Ignition ON, verify DTC P0461, P0462, P0463, or P0464 is not set.
If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
Circuit/System Testing
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 listed below and ground.
* Low Reference Terminal B (5.3L)
* Low Reference Terminal C (4.3L, 4.8L or 6.0L)
* Low Reference Terminal C (6.6L Diesel)
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Install a Signal Generator and Instrument Panel Tester between the signal circuit terminal and the low reference circuit terminal listed below:
* Signal Terminal C (5.3L)
* Low Reference Terminal B (5.3L)
* Signal terminal B (4.3L, 4.8L or 6.0L)
* Low Reference Terminal C (4.3L, 4.8L or 6.0L)
* Signal Terminal B (6.6L Diesel)
* Low Reference Terminal C (6.6L Diesel)
4. Ignition ON, vary the signal generator resistance between 40-250 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 circuits test normal, replace the ECM.
5. Vary the signal generator resistance between 40-250 ohms. Verify that the fuel gauge displays a range that varies between empty and full as the signal generator resistance changes.
• If the gauge 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 connectors at the fuel level sensor.
2. Sweep the fuel level sensor through its full range of motion while measuring resistance between the signal terminal and the low reference terminal listed below:
* Signal Terminal C (5.3L)
* Low Reference Terminal B (5.3L)
* Signal terminal B (4.3L, 4.8L or 6.0L)
* Low Reference Terminal C (4.3L, 4.8L or 6.0L)
* Signal Terminal B (6.6L Diesel)
* Low Reference Terminal C (6.6L Diesel)
3. Test for a minimum resistance value of 37-43 ohms and a maximum value of 245-255 ohms without any spikes or dropouts.
• If minimum resistance is not 37-43 ohms, maximum resistance is not 245-255 ohms, or if there are any spikes or dropouts
Replace the fuel level sensor.
• If minimum resistance is 37-43 ohms, maximum resistance is 245-255 ohms, and if there are no spikes or dropouts
4. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Fuel Level Sensor Replacement Service and Repair for the 4.3L engine
* Fuel Level Sensor Replacement Service and Repair for the 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L engine
* Fuel Level Sensor Replacement Service and Repair for the 6.6L engine
* Control Module References Control Module References for the ECM or IPC replacement, programming and setup