Buick Regal: DTC P0090-P0092, P00C8, P00C9, or P00CA

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 P0090

Fuel Pressure Regulator Control Circuit

DTC P0091

Fuel Pressure Regulator Control Circuit Low Voltage

DTC P0092

Fuel Pressure Regulator Control Circuit High Voltage

DTC P00C8

Fuel Pressure Regulator High Control Circuit

DTC P00C9

Fuel Pressure Regulator High Control Circuit Low Voltage

DTC P00CA

Fuel Pressure Regulator High Control Circuit High Voltage

Diagnostic Fault Information

Circuit/System Description

The high fuel pressure necessary for direct injection is supplied by the high pressure fuel pump. The high pressure fuel pump is mounted on the rear of the engine and is driven by a three-lobe cam on the camshaft. This high pressure fuel pump also regulates the fuel pressure using an actuator in the form of an internal solenoid-controlled valve. In order to keep the engine running efficiently under all operating conditions, the engine control module (ECM) requests pressure ranging from 2 - 15 MPa (290 - 2, 176 psi), depending on engine speed and load. Output drivers in the ECM provide the pump control circuit with a 12 V pulse-width modulated (PWM) signal, which regulates fuel pressure by closing and opening the control valve at specific times during pump strokes. This effectively regulates the portion of each pump stroke that is delivered to the fuel rail.

It is important to note that the high pressure fuel pump is a trailing-edge control system, meaning that if the control solenoid is NOT powered, the pump operates at maximum flow rate. In the event of pump control failure, the high pressure system is protected by a relief valve in the pump that prevents the pressure from exceeding 17.5 MPa (2, 538 psi).

NOTE: The fuel rail pressure sensor is diagnosed separately from the fuel pressure control system and should not be replaced for any codes referenced in this document.

The fuel rail fuel pressure sensor operates on a 5 V reference circuit and it provides the feedback necessary to the ECM to control the high pressure fuel pump and the fuel injectors.

Conditions for Running the DTC

• The ignition voltage is greater than 11 V.
• The engine speed is greater than 50 RPM.
• The DTCs run continuously within the enabling conditions.

Conditions for Setting the DTC

P0090

• The ECM detects an open circuit in the high pressure fuel pump actuator low control circuit.
• The DTC sets when the above condition is present for 4 s.

P0091

• The ECM detects a short to ground in the high pressure fuel pump actuator low control circuit.
• The DTC sets when the above condition is present for 4 s.

P0092

• The ECM detects a short to voltage in the high pressure fuel pump actuator low control circuit.
• The DTC sets when the above condition is present for 4 s.

P00C8

• The ECM detects an open circuit in the high pressure fuel pump actuator high control circuit.
• The DTC sets when the above condition is present for 4 s.

P00C9

• The ECM detects a short to ground in the high pressure fuel pump actuator high control circuit.
• The DTC sets when the above condition is present for 4 s.

P00CA

• The ECM detects a short to voltage in the high pressure fuel pump actuator high control circuit.
• The DTC sets when the above condition is present for 4 s.

Action Taken When the DTC Sets

• DTCs P0090, P0091, P0092, P00C8, P00C9, and P00CA are Type A DTCs.
• A message center or an indicator displays Reduced Engine Power.

Conditions for Clearing the DTC

• DTCs P0090, P0091, P0092, P00C8, P00C9, and P00CA are Type A DTCs.

Diagnostic Aids

• Before performing any circuit testing, ensure that the harness connector for the G18 High Pressure Fuel Pump is properly seated.
• Before performing any circuit testing, visually inspect the harness connector and the G18 High Pressure Fuel Pump connector for damage or bent pins.
• Circuit faults in the high pressure fuel control system may result in performance diagnostic failures, such as P0089, P00C6, P163A, P228C, or P228D. If any of the circuit DTCs referenced in this document are active, they take priority over any fuel system performance diagnostic.

  Always attempt to diagnose and repair circuit faults first, before reviewing other system DTCs.

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 P0685 or P1682 is not set.

• If any of the DTCs are set

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

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

3. Command the Fuel Pressure Regulator ON and OFF with a scan tool while observing the following control circuit status parameters:

• Fuel Pressure Regulator Control Circuit High Voltage Test Status
• Fuel Pressure Regulator Control Circuit Open Test Status
• Fuel Pressure Regulator Control Circuit Low Voltage Test Status
• Fuel Pressure Regulator High Control Circuit High Voltage Test Status
• Fuel Pressure Regulator High Control Circuit Open Test Status
• Fuel Pressure Regulator High Control Circuit Low Voltage Test Status
• If Malfunction is displayed

Refer to Circuit/System Testing

• Go to next step: If OK or Not Run is displayed

4. 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.

5. 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

6. All OK

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the G18 High Pressure Fuel Pump.

2. Ignition ON, verify that a test lamp does not illuminate between the high control circuit terminal 1 and ground and the low control circuit terminal 2 and ground.

• If the test lamp illuminates

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the appropriate control circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 Engine Control Module.

• Go to next step: If the test lamp does not illuminate

3. Verify that a test lamp does not illuminate between the high control circuit terminal 1 and B+ and the low control circuit terminal 2 and B+.

• If the test lamp illuminates

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the appropriate 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 control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If the test lamp does not illuminate

4. Connect a 3 A fused jumper wire between the high control circuit terminal 1 and ground.

5. Verify the Fuel Pressure Regulator High Control Circuit Open Test Status transitions from Malfunction to OK and the Fuel Pressure Regulator High Control Circuit Low Voltage Test Status transitions from OK to Malfunction.

• The parameters do not change

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the high control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: The parameters change

6. Connect a 3 A fused jumper wire between the low control circuit terminal 2 and B+.

7. Verify the Fuel Pressure Regulator Control Circuit Open Test Status transitions from Malfunction to OK and the Fuel Pressure Regulator Control Circuit High Voltage Test Status transitions from OK to Malfunction.

• The parameters do not change

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the low control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: The parameters change

8. Test or replace the G18 High Pressure Fuel Pump.

Component Testing

1. Ignition OFF, disconnect the harness connector at the G18 High Pressure Fuel Pump.

NOTE: The DMM and test leads must be calibrated to 0 Ω in order to prevent misdiagnosis.

2. Test for 0.3 - 0.7 Ω at 20ºC (68ºF) between the high control circuit terminal 1 and the low control circuit terminal 2.

• If not between 0.3 - 0.7 Ω

Replace the G18 High Pressure Fuel Pump.

• Go to next step: If between 0.3 - 0.7 Ω

3. Test for infinite resistance between each terminal and the G18 High Pressure Fuel Pump housing.

• If less than infinite resistance

Replace the G18 High Pressure Fuel Pump.

• Go to next step: If infinite resistance

4. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Fuel Pump Replacement
• Control Module References for K20 Engine Control Module replacement, setup, and programming
• Perform the Fuel Rail Pressure Relief Valve Reset procedure, if supported on the scan tool.

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