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 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 Fuel Gauge.
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 Fuel Gauge
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
1. Ignition ON, observe the scan tool Fuel Level Sensor parameter. The reading should be between 4-98 percent and vary with fuel level.
2. Ignition ON, perform the Instrument Cluster Gauge Sweep test with the scan tool, verify that the fuel level gauge sweeps from its low to high position
• If the fuel level gauge does not sweep, replace the P16 Instrument Cluster
3. Command the All Indicators test ON and OFF with the scan tool, verify that the low fuel level indicator turns ON and OFF.
• If the low fuel level indicator always stays on or always off, replace the P16 Instrument Cluster.
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 B46A primary and B46B secondary fuel level sensor.
2. Ignition OFF for 60 seconds, test for less than 5 ohm between the low reference circuit terminals listed below and ground.
* Primary terminal 1
* Secondary terminal A
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
3. Ignition ON, test for 4.8-5.2 V between the signal circuit terminals listed below and ground.
* Primary terminal 1
* Secondary terminal A
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Install a jumper wire between the signal circuit terminal 1 and A.
5. Install the Instrument Panel Tester between the jumped signal circuits and the low reference circuit. Verify the Instrument Panel Tester resistance is set at 40-250 ohm before turning the ignition ON.
• If not displaying the specified range, test both signal circuits for an open/high resistance. If the circuits test normal, replace the ECM.
6. Ignition ON, verify that the scan tool Fuel Tank Level Remaining parameter varies between 5 and 95 percent as the Instrument Panel Tester resistance is varied between 40 and 250 ohm.
• If not within the specified range, replace the K20 ECM.
7. While varying the Instrument Panel Tester resistance between 40 and 250 ohm verify the fuel gauge moves between empty and full.
• If not within the specified range, replace the fuel gauge.
8. If all circuits test normal, test or replace the appropriate B46 fuel level sensor.
Component Testing
Note: If equipped, the following tests can be performed at an inline connector. See schematics for the corresponding terminals to test at.
Static Test
1. Ignition OFF, disconnect the harness connector at the appropriate B46 fuel level sensor.
2. Test for 40-250 ohm between the signal terminal and the low reference terminal listed below.
* B46A fuel level sender Terminal 1 and 4.
* B46B fuel level sender Terminal A and D.
• If not within the specified range, replace the B46 fuel level sender.
Dynamic Test
1. Ignition OFF, disconnect the harness connector at the appropriate B46 fuel level sensor.
2. Remove the B46 fuel level sender from the fuel tank.
3. Sweep the sensor through the entire range while monitoring the resistance between the signal terminal and the low reference terminal listed below. The resistance should vary between less than 45 ohm and greater than 250 ohm without any spikes or dropouts.
* B46A fuel level sender Terminal 1 and 4.
* B46B fuel level sender Terminal A and D.
• If not within the specified range or is erratic, replace the B46 fuel level sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Fuel Level Sensor Replacement - Right Side Fuel Level Sensor Replacement - Right Side for the 3.6L engine
* Fuel Level Sensor Replacement - Left Side Fuel Level Sensor Replacement - Left Side for the 3.6L engine
* Fuel Level Sensor Replacement - Right Side Fuel Level Sensor Replacement - Right Side for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engines
* Fuel Level Sensor Replacement - Left Side Fuel Level Sensor Replacement - Left Side for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engines
* Control Module References Control Module References for ECM and IPC replacement, setup, and programming