Fuel Gauge Inaccurate or Inoperative (Dual Tank)
Fuel Gauge Inaccurate or Inoperative (Dual Tank)
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 sensor and the secondary fuel level sensor change resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the primary fuel level sensor, the secondary 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 fuel 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 tanks are full, the sensor resistances of both fuel level sensors are low and the ECM senses a low signal voltage on both the signal circuits of the primary fuel level sensor and the secondary fuel level sensor. When the fuel tanks are empty, the resistances of the fuel level sensors are high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the primary fuel level sensor and the secondary 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 Connector End Views By Name
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, verify DTC P0461, P0462, P0463, P0464, P2066, P2067, or P2068 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 primary and secondary fuel level sensors.
2. Ignition OFF, test for less than 1.0 ohms between the primary fuel level sensor low reference circuit terminal B and ground.
• 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. Ignition OFF, test for less than 1.0 ohms between the secondary fuel level sensor low reference circuit terminal B and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
4. Jumper the primary fuel level sensor signal circuit terminal C to secondary fuel level sensor signal circuit terminal C. Install a signal generator and instrument panel tester between the jumped signal circuits and ground.
5. Ignition ON, vary the signal generator resistance between 40-250 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 both signal circuits for an open/high resistance. If the circuits test normal, replace the ECM.
6. 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.
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 each fuel level sensor through its full range of motion while measuring resistance between the signal terminal C and the low reference terminal B.
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 repair.
* Fuel Level Sensor Replacement for the 6.0L (LFA) engine
* Fuel Level Sensor Replacement (2500 - 98.4L (26 gal) Tank - Front) Fuel Level Sensor Replacement (2500 - 98.4L (26 gal) Tank - Front)Fuel Level Sensor Replacement (1500 Series) Fuel Level Sensor Replacement (1500 Series)Fuel Level Sensor Replacement (1500 Series w/E85) Fuel Level Sensor Replacement (1500 Series w/E85)Fuel Level Sensor Replacement (2500 - 43.5L (11.5 gal) Tank - Rear) Fuel Level Sensor Replacement (2500 - 43.5L (11.5 gal) Tank - Rear) for the 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L engine
* Control Module References Control Module References for the ECM or IPC replacement, programming and setup