Buick Regal: DTC P0231, P0232, or P023F

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 P0231

Fuel Pump Control Circuit Low Voltage

DTC P0232

Fuel Pump Control Circuit High Voltage

DTC P023F

Fuel Pump Control Circuit

Diagnostic Fault Information

Circuit/System Description

The engine control module (ECM) supplies voltage to the fuel pump driver control module when the ECM detects that the ignition is on. The voltage from the ECM to the fuel pump driver control module remains active for 2 s, unless the engine is in crank or run. While this voltage is being received, the fuel pump driver control module supplies a varying voltage to the fuel tank fuel pump module in order to maintain the desired fuel line pressure.

Conditions for Running the DTC

P0231

• The ignition voltage is between 9 - 32 V.
• The fuel pump enable circuit is commanded ON.
• The fuel pump current is less than 100 A.

P0232

• The ignition voltage is between 9 - 32 V.
• The fuel pump enable circuit is commanded OFF.
• The above conditions are met for 4 s.
• The DTC runs once per trip.

P023F

• The ignition voltage is between 9 - 32 V.
• The fuel pump enable circuit is commanded ON.

Conditions for Setting the DTC

P0231

The fuel pump driver control module detects that the fuel pump current is greater than 14.48 A for 1 s.

P0232

The fuel pump driver control module detects that the fuel pump control circuit voltage is greater than 3.86 V for 0.5 s when the voltage should be 0 V.

P023F

The fuel pump driver control module detects that the fuel pump current is less than 0.5 A and the fuel pump duty cycle is greater than 20 percent for 1 s.

Action Taken When the DTC Sets

• DTCs P0231 and P023F are Type A DTCs.
• DTC P0232 is a Type B DTC.

Conditions for Clearing the DTC

• DTCs P0231 and P023F are Type A DTCs.
• DTC P0232 is a Type B DTC.

Diagnostic Aids

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

On vehicles equipped with a high pressure mechanical pump on Direct Fuel Injection engines, the vehicle may continue to run even though the pump in the fuel tank is not operating.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Description and Operation

Fuel System Description

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

1. Ignition ON.

2. Verify the fuel pump turns ON and OFF when commanding the Fuel Pump Enable On and Off with a scan tool.

• If the fuel pump does not turn ON and OFF

Refer to Circuit/System Testing.

• Go to next step: If the fuel pump turns ON and OFF

3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

4. Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

5. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the K111 Fuel Pump Driver Control Module and the X350 inline harness connector.

2. Test for less than 2 Ω in the low reference circuit end to end between the appropriate terminal at the body side of connector X350 and at the K111 Fuel Pump Driver Control Module.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

3. Connect the harness connector at the K111 Fuel Pump Driver Control Module.

4. Ignition ON, connect a test lamp between the fuel pump control circuit terminal and the low reference circuit terminal at the body side of connector X350.

5. Verify the test lamp turns ON and OFF when commanding the Fuel Pump Enable On and Off with a scan tool.

• If the test lamp is always OFF

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

• If the test lamp is always ON

1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K111 Fuel Pump Driver Control Module, ignition ON.
2. Test for less than 1 V between the fuel pump control circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, test or replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If the test lamp turns ON and OFF

6. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the K111 Fuel Pump Driver Control Module and at the G12 Fuel Pump. It may take up to 2 minutes for all vehicle systems to power down.

7. Test for infinite resistance between the low reference circuit and ground.

• If less than infinite resistance

Repair the short to ground on the circuit.

• Go to next step: If infinite resistance

8. 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.

• Go to next step: If less than 2 Ω

9. Test for infinite resistance between the fuel pump control circuit and ground.

• If less than infinite resistance

Repair the short to ground on the circuit.

• Go to next step: If infinite resistance

10. Test for less than 2 Ω in the fuel pump control circuit end to end.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

11. Replace the G12 Fuel Pump.

Component Testing

Static Test

1. Ignition OFF, disconnect the harness connector at the K111 Fuel Pump Driver Control Module.

2. Connect a DMM, set on the diode setting, with the positive lead at terminal 16 and the negative lead at terminal 9 of the K111 Fuel Pump Driver Control Module 3. Test for 0.4 - 0.8 V between terminal 16 and terminal 9.

• If not between 0.4 - 0.8 V

Replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If between 0.4 - 0.8 V

4. Connect a DMM, set on the diode setting, with the positive lead at terminal 9 and the negative lead at terminal 16 of the K111 Fuel Pump Driver Control Module 5. Test for OL between terminal 9 and terminal 16.

• If not OL

Replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If OL

6. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Fuel Pump Power Control Module Replacement (AWD) or Fuel Pump Power Control Module Replacement (FWD) for K111 Fuel Pump Driver Control Module replacement
• Fuel Tank Fuel Pump Module Replacement (FWD) or Fuel Tank Fuel Pump Module Replacement (AWD) for G12 Fuel Pump replacement

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