Buick Regal: Fuel Gauge Malfunction (FWD)

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0461

Fuel Level Sensor Performance

DTC P0462

Fuel Level Sensor Circuit Low Voltage

DTC P0463

Fuel Level Sensor Circuit High Voltage

DTC P0464

Fuel Level Sensor Circuit Intermittent

Diagnostic Fault Information

1. Fuel Gauge Malfunction

Circuit/System Description

The fuel level sensor changes resistance based on fuel level and is wired to the Fuel Pump Driver Control Module. The Fuel Pump Driver Control Module sends the fuel level sensor reading to the Engine Control Module (ECM) via serial data. The ECM monitors the fuel level sensor signal in order to determine the fuel level. When the fuel tank is full, the resistances of the fuel level sensor is low and the ECM senses a low signal voltage on the signal circuit of the fuel level sensor. When the fuel tank is empty, the resistance of the fuel level sensor 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 serial data to the body control module (BCM).

The BCM then sends the fuel level percentage via serial data to the instrument cluster in order to control the fuel gauge. When the fuel level falls below approximately 11% the instrument cluster illuminates the low fuel level indicator.

Conditions for Running the DTC

• Ignition ON
• Battery voltage is between 11 - 32 V

Conditions for Setting the DTC

P0461

• The ECM detects a difference between the fuel consumed by the engine and change of the fuel level signal of less than 1 L (0.26 gal) over a range of 30 L (7.92 gal) or 45.6% of the primary fuel tank.
• The above condition is present for about 300 seconds.

P0462

• The signal voltage is less than 0.25 V.
• The above conditions must be met for 5 seconds.

P0463

• The signal voltage is greater than 4.7 V.
• The above conditions must be met for 5 seconds.

P0464

• The fuel level change is greater than 10% for a duration lasting less than 30 seconds.
• DTC P0464 runs and fails 2 out of 3 test cycles.

Action Taken When the DTC Sets

P0461, P0462, and P0463

• P0461, P0462, and P0463 are Type B DTCs
• The fuel gauge defaults to empty
• The low fuel indicator illuminates

P0464

• P0464 is a Type A DTC

Conditions for Clearing the DTC

• P0461, P0462, and P0463 are Type B DTCs
• P0464 is a Type A DTC

Reference Information

Schematic Reference

Instrument Cluster Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEW INDEX

Description and Operation

Instrument Cluster Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

Without UDV

1. Ignition ON.

2. Verify the fuel level gauge sweeps when performing the scan tool Instrument Cluster Gauge Sweep control function.

• If the fuel level gauge does not sweep

Replace the P16 Instrument Cluster

• Go to next step: If the fuel level gauge sweeps

3. Verify the low fuel level indicator turns ON and OFF when commanding the scan tool All Indicators control function ON and OFF.

• If the low fuel level indicator does not turn ON and OFF

Replace the P16 Instrument Cluster

• Go to next step: If the low fuel level indicator turns ON and OFF

4. Verify the scan tool Fuel Level Sensor parameter is between 0.5 - 3.5 V and varies with fuel level.

• If not between 0.5 - 3.5 V or does not vary with fuel level

Refer to Circuit/System Testing

• Go to next step: If between 0.5 - 3.5 V and varies with fuel level

5. All OK.

With UDV

1. Ignition ON.

2. Verify the scan tool Fuel Level Sensor parameter is between 0.5 - 3.5 V and varies with fuel level.

• If not between 0.5 - 3.5 V or does not vary with fuel level

Refer to Circuit/System Testing

• Go to next step: If between 0.5 - 3.5 V and varies with fuel level

3. All OK.

Circuit/System Testing

NOTE: Circuit/System Verification must be performed before proceeding with Circuit/System Testing.

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the A7 Fuel Pump and Level Sensor Assembly. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 Ω between the low reference circuit terminal 2 and ground.

• If 10 Ω or greater

1. Ignition OFF, disconnect the harness connector at the K111 Fuel Pump Driver Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Verify the scan tool Fuel Level Sensor Left Tank parameter is greater than 4.8 V.

• If 4.8 V or less

1. Ignition OFF, disconnect the harness connector at the K111 Fuel Pump Driver Control Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If greater than 4.8 V

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2.

6. Verify the scan tool Fuel Level Sensor Left Tank parameter is less than 0.2 V.

• If 0.2 V or greater

1. Ignition OFF, disconnect the harness connector at the K111 Fuel Pump Driver Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Ignition OFF
4. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If less than 0.2 V

7. Test or replace the B46 Fuel Level Sensor.

8. Operate the vehicle within the Conditions for Running the DTC.

9. Verify the condition does not return.

• If the condition returns

Replace the K20 Engine Control Module.

• Go to next step: If the condition does not return

10. All OK.

Component Testing

1. Ignition OFF, remove the fuel level sensor.

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 2.

3. Test for a minimum resistance value of 37-43 Ω and a maximum value of 245-255 Ω without any spikes or dropouts.

• If minimum resistance is not 37-43 Ω, maximum resistance is not 245-255 Ω, or if there are any spikes or dropouts

Replace the fuel level sensor.

• Go to next step: If minimum resistance is 37-43 Ω, maximum resistance is 245-255 Ω, and if there are no spikes or dropouts

4. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Displays and Gauges Component Replacement Reference
• Control Module References for control module replacement, programming, and setup.

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