Buick Regal: DTC P2635 or P2BB3

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 Descriptor

DTC P2635

Fuel Pump Flow Performance

DTC P2BB3

Fuel Pump Feedback Performance

Circuit/System Description

The engine control module (ECM) supplies voltage to the fuel pump power control module when the ECM detects that the ignition is on. The voltage from the ECM to the fuel pump power control module remains active for 2 s, unless the engine is in crank or run. While this voltage is being received, the fuel pump power control module closes the ground switch of the fuel pump. The fuel pump power control module maintains correct fuel pressure based on the information from the fuel pressure sensor and varying the Pulse Width Modulation (PWM) controlled current to the fuel pump.

Conditions for Running the DTC's

DTC P2635

• DTC P018B, P018C, P018D, P0231, P0232, P023F, P0641 or P1255 are not active.

  Fuel pump control is enabled, the fuel pump control state and pressure control state are normal.

• The ignition voltage is between 11 - 32 V.
• The engine has been running for greater than 30 s.
• The engine fuel flow is not 0.
• Low fuel level warning not present.
• The DTC runs continuously when the conditions above are met.

DTC P2BB3

• The ignition voltage is greater than 11 V
• The fuel pump duty cycle command measured and received is in error for greater than 0.1 s
• The DTC runs continuously when the conditions above are met.

Conditions for Setting the DTC's

The fuel pump power control module detects a difference of ÂÂ+- 60 kPa at 400 kPa request or ÂÂ+-45 kPa at 300 kPa request between the desired fuel pressure and the actual fuel pressure for approximately 10 s.

Action Taken When the DTC Sets

DTC P2635 is a Type B DTC.

DTC P2BB3 is a Type A DTC.

Conditions for Clearing the DTC

DTC P2635 is a Type B DTC.

DTC P2BB3 is a Type A 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

Powertrain Component View

Powertrain Component Views

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 DTC U0074 or U18A2 is not set or stored in history.

• If DTC U0074 or U18A2 is set or stored in history

Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• Go to next step: If DTC U0074 or U18A2 is not set or stored in history

3. Verify that DTC P018B, P018C, P018D, P0231, P0232, or P023F is not set.

• If any of the DTCs are set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• Go to next step: If none of the DTCs are set

4. Verify the scan tool Short Term Fuel Pump Trim and the Long Term Fuel Pump Trim when multiplied together are less than 1.5.

• If greater than 1.5

Refer to Circuit/System Testing.

• Go to next step: If less than 1.5

5. Command the Fuel Pressure to 300 kPa (43.5 PSI) using the scan tool Control Function: Fuel Pressure Increase/Decrease.

6. Verify the scan tool parameter: Fuel Pressure Sensor & Desired Fuel Pressure are within 45 kPa (6.5 PSI) of each other at 300 kPa (43.5 PSI) request.

• If greater than 45 kPa (6.5 PSI)

Refer to Circuit/System Testing.

• Go to next step: If less than 45 kPa (6.5 PSI)

7. Command the Fuel Pressure to 400 kPa (58 PSI) using the scan tool Control Function: Fuel Pressure Increase/Decrease.

8. Verify the scan tool parameter: Fuel Pressure Sensor & Desired Fuel Pressure are within 60 kPa (8.7 PSI) of each other at 400 kPa (58 PSI) request.

• If greater than 60 kPa (8.7 PSI)

Refer to Circuit/System Testing.

• Go to next step: If less than 60 kPa (8.7 PSI)

9. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset.

You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

10. 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

11. All OK.

Circuit/System Testing

NOTE: Do not replace the fuel pump power control module based on a history DTC P2635. DTC P2635 may be stored but that does not indicate a failure of the fuel pump power control module. Refer to Strategy Based Diagnosis for further history DTC diagnostics.

1. Verify the proper fuel system pressure. Refer to Fuel System Diagnosis.

• If the fuel pressure is not normal

Repair the fuel system as necessary.

• Go to next step: If the fuel pressure is normal

2. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Fuel Feed Front Pipe Replacement
• Fuel Feed Pipe Replacement - Underbody
• Fuel Injector Replacement
• Fuel Tank Fuel Pump Module Replacement (FWD) or Fuel Tank Fuel Pump Module Replacement (AWD)
• Perform the Fuel Pump Trim Reset procedure with a scan tool after the repair.

Repair Verification

1. Install any components that have been removed or replaced during diagnosis.

2. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.

3. Clear the DTCs with a scan tool.

4. Turn OFF the ignition for 60 s.

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

6. Verify the scan tool Short Term Fuel Pump Trim and the Long Term Fuel Pump Trim when multiplied together are less than 1.5.

• If greater than 1.5

Refer to Circuit/System Testing.

• Go to next step: If less than 1.5

7. Command the Fuel Pressure to 300 kPa (43.5 PSI) using the scan tool Control Function: Fuel Pressure Increase/Decrease.

8. Verify the scan tool parameter: Fuel Pressure Sensor & Desired Fuel Pressure are within 45 kPa (6.5 PSI) of each other at 300 kPa (43.5 PSI) request.

• If greater than 45 kPa (6.5 PSI)

Refer to Circuit/System Testing.

• Go to next step: If less than 45 kPa (6.5 PSI)

9. Command the Fuel Pressure to 400 kPa (58 PSI) using the scan tool Control Function: Fuel Pressure Increase/Decrease.

10. Verify the scan tool parameter: Fuel Pressure Sensor & Desired Fuel Pressure are within 60 kPa (8.7 PSI) of each other at 400 kPa (58 PSI) request.

• If greater than 60 kPa (8.7 PSI)

Refer to Circuit/System Testing.

• Go to next step: If less than 60 kPa (8.7 PSI)

11. All OK.

READ NEXT: