Fuel Gauge Inaccurate or Inoperative
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 sender changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit 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 primary and the secondary fuel level sender resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the primary and the secondary fuel level sender resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the primary and secondary fuel level sender in order to calculate the percentage of remaining fuel in the tanks. The ECM sends the fuel level information via serial data circuit to the instrument panel cluster (IPC) for display in the fuel gauge.
Reference Information
Schematic Reference
Instrument Cluster Schematics Instrument Cluster Schematics
Connector End View Reference
Component Connector End Views Folding Top 5 Bow Lowered Switch (CM7)
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 Verification
Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4-98 percent.
Circuit/System Testing
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 low reference circuit terminal 4 and ground.
• If greater than the specified range, test the circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition OFF, test for less than 1 ohm between the secondary low reference circuit terminal 4 and ground.
• If greater than the specified range, test the circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
4. Jumper the primary fuel level sensor signal circuit terminal 1 to the secondary fuel level sensor signal circuit terminal 1. Install a Signal Generator and Instrument Panel Tester between the jumped signal circuits and the low reference circuit terminal 4.
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 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 gauge is incorrect, replace the 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 fuel level senders.
2. Sweep the fuel level sensor through its full range of motion while measuring resistance between the signal terminal 1 and the low reference terminal 4.
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 appropriate 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 diagnostic procedure.
* Fuel Level Sensor Replacement - Left Side Fuel Level Sensor Replacement - Left Side
* Fuel Level Sensor Replacement - Right Side Fuel Level Sensor Replacement - Right Side
* Control Module References Control Module References for the ECM replacement, setup, and programming