P0091
DTC P0090-P0092, P00C8, P00C9, or P00CA
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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 pump is mounted on the rear of the engine and is driven by a three-lobe cam on the Bank 2 exhaust camshaft. This 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 to 15 MPa (290 to 2176 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 (2538 psi).
The fuel rail 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. 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.
Conditions for Running the DTC
* The ignition voltage is between 11-18 V.
* 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 DTC's.
Reference Information
Schematic Reference
Engine Controls Schematics (LFX) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Fuel System Description Fuel System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Observe the DTC information with a scan tool. DTC P0090, P0091, P0092, P00C8, P00C9, P00CA, P0685, or P1682 should not set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Ignition ON, 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
• Each parameter should toggle between OK and Not Run or Not Run and OK.
3. Engine idling, observe the Fuel Rail Pressure Sensor parameter with a scan tool. The pressure should be approximately 1.9-5.0 MPa (276-725 psi).
4. Command an increase and decrease in Fuel Pressure with a scan tool. Observe the scan tool Fuel Rail Pressure Sensor parameter. The Fuel Rail Pressure Sensor should increase or decrease with each command.
5. 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.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the G18 high pressure fuel pump.
2. Ignition OFF, verify that a test lamp does not illuminate between B+ and the low control circuit terminal 1.
• If the test lamp illuminates, test the low control circuit for a short to ground. If the circuit tests normal, replace the K20 engine control module.
3. Ignition ON, verify that a test lamp does not illuminate between ground and the high control circuit terminal 2.
• If the test lamp illuminates, test the high control circuit for a short to voltage. If the circuit tests normal, replace the K20 engine control module.
4. Ignition ON, command the Fuel Pressure Regulator ON with a scan tool. Verify that the test lamp illuminates.
• If the test lamp does not illuminate, test the high control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 engine control module.
5. Ignition OFF, connect a test lamp between the low control circuit terminal 1 and B+.
6. Ignition ON, command the Fuel Pressure Regulator ON with a scan tool. Verify that the test lamp illuminates.
• If the test lamp does not illuminate, test the low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 engine control module.
7. If all circuits test normal, test or replace the G18 high pressure fuel pump.
Component Testing
Static Test
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 ohms in order to prevent misdiagnosis.
2. Test for 9-11 ohms at 25°C (77°F) between the low control circuit terminal 1 and the high control circuit terminal 2.
• If not within the specified range, replace the G18 high pressure fuel pump.
3. Measure the resistance between each terminal and the high pressure fuel pump housing. The DMM should display OL.
• If less than the specified value, replace the G18 high pressure fuel pump.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Fuel Pump Replacement Fuel Pump Replacement
* Control Module References Control Module References for ECM replacement, setup, and programming