VIN L
DTC P0087 or P0088
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 P0087
- Fuel Rail Pressure (FRP) Too Low
DTC P0088
- Fuel Rail Pressure (FRP) Too High
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The engine control module (ECM) controls the fuel rail pressure by controlling fuel pressure regulator 1 and fuel pressure regulator 2 simultaneously to achieve the desired fuel rail pressure. The ECM compares the desired fuel pressure that is calculated and the actual fuel pressure reading from the fuel pressure sensor and monitors these two values to detect faults in the fuel system. If the two pressures are above or below the set limit for greater than 8 seconds a DTC will set.
Conditions for Running the DTC
* Fuel tank level is greater than 15 %
* Engine is in crank or run mode
* Ambient air temperature is greater than -7° C (19° F)
* Ambient pressure is greater than 74.8 kPa
Conditions for Setting the DTC
P0087
The actual fuel rail pressure is more than 11 MPa (1,595 psi) below the desired fuel rail pressure for more than 8 s.
P0088
The actual fuel rail pressure is more than 20 MPa (2900 psi) above the desired fuel rail pressure for more than 8 s.
Action Taken When the DTC Sets
DTCs P0087 and P0088 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0087 and P0088 are Type B DTCs.
Diagnostic Aids
P0087
Note: If the Change Fuel Filter Warning light is ON with DTC P0087, inspect the fuel filter for a restriction or contamination.
* A restricted, kinked, or damaged fuel supply line may cause DTC P0087 to set.
* If a low fuel condition is present and DTC P0087 sets, inspect the fuel sender pickup tube for damage or perforations.
* Water or contaminated fuel may cause this DTC to intermittently set. Refer to Contaminants-in-Fuel Diagnosis (Contaminants-in-Fuel Diagnosis).
* When ambient temperatures are below 0°C (32°F), the fuel tank pickup screen may be iced over from water in the fuel tank.
* External high pressure fuel rail or line leaks 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.
* High fuel injector return flow may cause this DTC to set.
* The addition of fuel system enhancements, such as auxiliary fuel tanks or add on fuel filters may relate to driveability complaints.
P0088
* If the fuel system pressure is actually too high, a fuel knock may exist.
* A sticking fuel pressure regulator may cause this DTC to set.
* Restricted fuel return lines may cause the DTC to set.
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
Special Tools
CH-48027 Digital Pressure Gauge
Circuit/System Verification
1. Ignition ON, observe the scan tool DTC information. DTC P0090, P2294, P0191, P0263, P0266, P0269, P0272, P0275, P0278, P0281, or P0284 should not be set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle)
2. Operate the engine through varying loads while observing the fuel pressure difference between the Actual Fuel Rail Pressure and the Desired Fuel Rail Pressure with a scan tool. The difference should be less than 690 kPa (100 psi).
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: Because of the cleansing properties of the biodiesel, switching from the straight diesel to a biodiesel blend can prematurely restrict the fuel filter with normal deposits in the fuel system. A fuel filter replacement might be required sooner than the recommended interval.
P0087
1. Attempt to start the engine.
• If the engine does not start, refer to Engine Cranks But Does Not Run (Engine Cranks But Does Not Run).
2. Install the CH-48027 to the fuel rail service port. With the engine a idle, verify that the CH-48027 displays between 1-6 in Hg vacuum.
• If greater than the specified value, inspect for a restricted fuel filter, kinked, or restricted fuel supply lines. Refer to Fuel System Diagnosis (Fuel System Diagnosis)
3. Operate the vehicle within the conditions for which the customer concern occurs while observing the CH-48027 does not display greater than 14 in Hg vacuum. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records.
• If the CH-48027 displays greater than 14 in Hg vacuum, inspect for a restricted fuel filter, kinked, or restricted fuel supply lines. Refer to Fuel System Diagnosis (Fuel System Diagnosis)
• If within the specified value, refer to Fuel System Diagnosis - High Pressure Side (Fuel System Diagnosis - High Pressure Side)
P0088
Note:
* This procedure must be performed at idle and at 1800 RPM.
* 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. 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 fuel pressure regulator 1 and fuel pressure regulator 2. Inspect the fuel system for contamination, refer to Contaminants-in-Fuel Diagnosis (Contaminants-in-Fuel Diagnosis).
2. 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 Injection Pump Replacement (Fuel Injection Pump Replacement)
* Fuel Pressure Regulator Replacement (Service and Repair)
* Fuel Pressure Relief Valve Replacement (Service and Repair)