P128E
DTC P128E
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 Descriptor
DTC P128E
- Fuel Rail Pressure Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
During certain engine operating conditions the engine control module (ECM) checks the actual fuel rail pressure reported from the fuel rail pressure sensor and compares the value to a set programed value. If the values are out of the calibrated range for a set amount of time DTC P128E will set.
Conditions for Running the DTC
* Fuel tank level is greater than 15 %
* Engine is in crank or run mode
Conditions for Setting the DTC
* Actual fuel rail pressure is below 15 MPa (2175 psi) for greater than 6 s.
* Actual fuel rail pressure exceeds 215 MPa (31,183 psi) for greater than 1 s.
Action Taken When the DTC Sets
* DTC P128E is a Type A DTC.
* The ECM commands the engine to operate in the Reduced Engine Power mode.
* The message center displays Reduced Engine Power.
Conditions for Clearing the MIL/DTC
DTC P128E is a Type A DTC.
Diagnostic Aids
* Water in fuel system may cause this DTC to intermittently to set. Refer to Contaminants-in-Fuel Diagnosis (Contaminants-In-Fuel Diagnosis)
* Gasoline in fuel system may cause this DTC to set.
* When power enhancing devices have been attached to the fuel rail pressure sensor circuits, this DTC may set and adversely affect the fuel system components.
* The addition of fuel system enhancements, such as auxiliary fuel tanks or add on fuel filters may relate to driveability complaints.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning)for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify no other DTCs are set.
• If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) for further diagnosis.
2. Observe the Fuel Rail Pressure Sensor parameter with a scan tool. During engine cranking, the pressure should be at least 10 MPa (1450 psi). With the engine running at idle, the pressure should be close to the Desired Fuel Rail Pressure. As the engine speed increases, the Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure should closely match each other.
3. 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
Note:
* You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
* At idle fuel pressure regulator 2 is used to maintain the desired fuel pressure, if fuel pressure regulator 2 is leaking the actual pressure will be at least 690 kPa (100 psi ) below the desired fuel pressure. Running the engine above 1700 RPM switches the fuel pressure control mode to fuel pressure regulator 1. If fuel pressure regulator 1 is leaking or binding the fuel pressure will fluctuate above and below the desired fuel pressure by greater than 690 kPa (100 psi).
1. Review the freeze frame data and compare to the conditions to set this DTC.
• If the fuel pressure was low when this DTC set, refer to Fuel System Diagnosis - High Pressure Side (Fuel System Diagnosis - High Pressure Side)
Note: This procedure must be performed at idle and at 1800 RPM.
2. Engine at idle, command the fuel pressure incrementally through the entire fuel pressure range with a scan tool. The Actual Fuel Rail Pressure and the Desired Fuel Rail Pressure should be within 690 kPa (100 psi) for the entire fuel pressure range.
• If the desired and actual fuel pressure at idle is within 690 kPa (100 psi) and was not within 690 kPa (100 psi) at 1800 RPM, replace the Q45A fuel pressure regulator 1.
• If the desired and actual fuel pressure at idle was not within 690 kPa (100 psi) but was within 690 kPa (100 psi) at 1800 RPM, replace the Q45B fuel pressure regulator 2.
• If the desired and actual fuel pressure was not within 690 kPa (100 psi) at idle or at 1800 RPM, replace both Q45A fuel pressure regulator 1 and Q45B fuel pressure regulator 2. Inspect the fuel system for contamination, refer to Contaminants-in-Fuel Diagnosis (Contaminants-In-Fuel Diagnosis).
3. If all the components test normal, refer to Diagnostic Aids.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fuel Pressure Relief Valve Replacement (Service and Repair)
* Perform the scan tool Diesel Particulate Filter (DPF) Regeneration Enable (Diesel Particulate Filter (DPF) Regeneration Enable) procedure if the scan tool DPF Soot Mass is less than 30 g. If the scan tool DPF Soot Mass is 30 g or greater, perform the Diesel Particulate Filter (DPF) Service Regeneration (Diesel Particulate Filter (DPF) Service Regeneration) procedure.
* Control Module References (Programming and Relearning)for ECM replacement, programming, and setup.