Buick Regal: DTC P1176 or P1177

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 P1176

Fuel Pump Driver Control Module 5V Reference 1 Circuit

DTC P1177

Fuel Pump Driver Control Module 5V Reference 2 Circuit

Circuit/System Description

The Fuel Pump Driver Control Module has 2 internal 5V reference circuits. Each internal reference circuit provides external 5V reference circuits to one sensor. A short to ground or short to voltage on one external 5V reference circuit can affect the component connected to the same internal 5V reference circuit.

Conditions for Running the DTC

These DTCs run continuously when the ignition voltage is greater than 6.4 V.

Conditions for Setting the DTC

The Fuel Pump Driver Control Module detects a short to ground or voltage on any of the 5V reference circuits for greater than 0.5 s.

Action Taken When the DTC Sets

DTCs P1176, P1177 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P1176, P1177 are Type A DTCs.

Diagnostic Aids

P1176

The 5V reference 1 circuit provides 5 V circuits to the sensors listed below:

P1177

The 5V reference 2 circuit provides 5 V circuits to the sensors listed below:

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Component View Reference

Powertrain Component Views

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 scan tool 5V Reference 1-2 Circuit Status parameters do not display Malfunction.

• If any of the parameters display Malfunction

Refer to Circuit/System Testing.

• Go to next step: If none of the parameters display Malfunction

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

NOTE: Additional DTCs will set when disconnecting the components.

1. Ignition OFF, disconnect the harness connector at all appropriate sensors for the applicable DTC.

Refer to Diagnostic Aids.

2. Ignition ON.

3. Test for 4.8 - 5.2 V between one of the 5V reference circuits and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the harness connectors at the K111 Fuel Pump Driver Control Module.
2. Test for infinite resistance between the 5V reference circuit for each applicable component 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.

• If greater than 5.2 V

1. Ignition OFF, disconnect the harness connectors at the K111 Fuel Pump Driver Control Module.
2. Test for less than 1 V between the 5V reference circuit for each applicable component and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If between 4.8 - 5.2 V

NOTE: A short to voltage or ground on the signal circuit of certain components may cause this DTC to set.

4. Verify the appropriate scan tool 5V Reference 1, 2 Circuit Status parameter displays OK while connecting each component associated with the 5V reference circuit one at a time.

• If the parameter does not display OK when a component is connected

Test the signal circuit of that component for a short to ground or voltage. If the circuit tests normal, replace the component.

• Go to next step: If the parameter displays OK when all components are connected

5. 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)
• Control Module References for engine control module replacement, programming, and setup.

DTC P1178 or P1179

Diagnostic Instructions

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

DTC Descriptors

DTC P1178

Fuel Pump Driver Control Module Sensor 1 Internal Supply Circuit

DTC P1179

Fuel Pump Driver Control Module Sensor 2 Internal Supply Circuit

Circuit/System Description

The fuel pump power control module is in constant communication with the engine control module (ECM) regarding the operating state of the fuel pump power control system. Serial data messages are sent in a continuously repeating series of rolling counts with associated password protect samples. Each count/sample is assigned a value. When the ECM determines there is an error in the fuel pump control module fuel level sensor internal supply circuit, the ECM sets DTC P1178 or P1179.

Conditions for Running the DTC

• The ignition voltage is greater than 11 V.
• The DTC runs continuously when the above condition is met.

Conditions for Setting the DTC

The ECM detects an error value for over 1 s.

Action Taken When the DTC Sets

DTC P1178 and P1179 are Type A DTCs.

Conditions for Clearing the DTC

DTC P1178 and P1179 are Type A DTCs.

Diagnostic Aids

An intermittent fault in the CAN circuits will cause the ECM to set DTC P1178 or P1179.

Reference Information

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

NOTE:

• DTC P1178 and P1179 are informational DTCs.
• Diagnose all other engine control module DTCs prior to DTC P1178 or P1179.

1. Verify that no other DTCs are set except for DTC P1178 or P1179.

• If any other DTCs are set

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

• Go to next step: If only DTC P1178 or P1179 is set

2. Replace the K111 Fuel Pump Power Control Module.

3. Verify the DTC does not set while operating the vehicle within the Conditions for Running the DTC.

• If DTC sets

Replace the K20 Engine Control Module.

• Go to next step: If DTC does not set

4. 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 Power Control Module Replacement
• Control Module References for engine control module replacement, programming, and setup

DTC P1255

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 P1255

Fuel Pump Control Module Driver High Temperature

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 seconds, 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 pressure.

Conditions for Running the DTC

• The ignition voltage is between 7 - 32 V.
• The engine is cranking or running.
• The fuel pump enable circuit is commanded ON.
• The DTC runs continuously when the conditions above are met.

Conditions for Setting the DTC

The fuel pump driver control module detects a driver temperature greater than 302ºF (150ºC) for less than 0.5 s.

Action Taken When the DTC Sets

DTC P1255 is a Type A DTC.

Conditions for Clearing the DTC

DTC P1255 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.

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 DTC 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

3. Verify that the area where the K111 Fuel Pump Driver Control Module is located is free of debris, clutter, or any insulating material that would cause the fuel pump driver control module to overheat.

• If any debris, clutter, or other material is found

1. Clear the area where the K111 Fuel Pump Driver Control Module is located.
2. Clear the DTC and test drive the vehicle.
3. Verify DTC P1255 is not set.
   • If DTC P1255 is set, replace the K111 Fuel Pump Driver Control Module.
   • Go to next step: If DTC P1255 is not set
4. All OK.

• Go to next step: If no debris, clutter, or other material is found

4. Clear the DTC and test drive the vehicle.

5. Verify DTC P1255 is not set.

• If DTC P1255 is set

Replace the K111 Fuel Pump Driver Control Module.

• Go to next step: If DTC P1255 is not set.

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).

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