P0088-FUEL RAIL PRESSURE TOO HIGHFor a complete wiring diagram Refer to Section 8WWhen Monitored:With the engine running.Set Condition:The ECM determines that the fuel rail pressure is too high for a given engine speed and load.
Possible CausesAIR IN FUEL SYSTEMFUEL DELIVERY SYSTEMFUEL PRESSURE SENSORFUEL INJECTOR(S)FUEL PRESSURE SOLENOIDFUEL PUMPFUEL SYSTEM CONTAMINATIONFUEL SYSTEM LEAKINTERMITTENT DTC
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)Diagnostic Test1.CHECKING FOR OTHER ECM DTCSHIGH-PRESSURE FUEL LINES DELIVER DIESEL FUEL UNDER EXTREME PRESSURE FROM THE INJECTION PUMP TO THE FUEL INJECTORS. THIS MAY BE AS HIGH AS 23,200 PSI (1600 BAR). USE
EXTREME CAUTION WHEN INSPECTING FOR HIGH-PRESSURE FUEL LEAKS.FUEL UNDER THIS AMOUNT OF PRESSURE CAN PENETRATE SKIN CAUSING PERSONAL INJURY OR DEATH. INSPECT FOR HIGH-PRESSURE FUEL LEAKS WITH A SHEET OF CARDBOARD. WEAR SAFETY
GOGGLES AND ADEQUATE PROTECTIVE CLOTHING WHEN SERVICING FUEL SYSTEM.Turn the ignition on.With the scan tool, read the ECM DTCs.Are there any other DTCs present?YesRefer to symptom list for problems related to the DTC other than this DTC.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 22.CURRENT DTCRefer to the Service Information and perform the Air Bleed Procedure before continuing diagnosis.Turn the ignition on.With the scan tool, erase the ECM DTCs.Driving the vehicle up and down steep hills or rapid cornering with a low fuel level can cause this DTC to set. Verify with customer if Low Fuel Light was illuminated
when fault occurred.Test drive the vehicle under various load and speed conditions to attempt to duplicate the fault.With the scan tool, read the ECM DTCs.Does the scan tool display this DTC?YesGo To 3NoRefer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.(Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)3.FUEL SYSTEM LEAKTurn the ignition off.HIGH-PRESSURE FUEL LINES DELIVER DIESEL FUEL UNDER EXTREME PRESSURE FROM THE INJECTION PUMP TO THE FUEL INJECTORS. THIS MAY BE AS HIGH AS 23,200 PSI (1600 BAR). USE
EXTREME CAUTION WHEN INSPECTING FOR HIGH-PRESSURE FUEL LEAKS.FUEL UNDER THIS AMOUNT OF PRESSURE CAN PENETRATE SKIN CAUSING PERSONAL INJURY OR DEATH. INSPECT FOR HIGH-PRESSURE FUEL LEAKS WITH A SHEET OF CARDBOARD. WEAR SAFETY
GOGGLES AND ADEQUATE PROTECTIVE CLOTHING WHEN SERVICING FUEL SYSTEM.Inspect the entire fuel system for leakage.Is there any evidence of leakage?YesRepair as necessary in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 44.FUEL SYSTEM CONTAMINATIONMixing any other fuels such as gasoline or kerosine can cause this DTC to set.HIGH-PRESSURE FUEL LINES DELIVER DIESEL FUEL UNDER EXTREME PRESSURE FROM THE INJECTION PUMP TO THE FUEL INJECTORS. THIS MAY BE AS HIGH AS 23,200 PSI (1600 BAR). USE
EXTREME CAUTION WHEN INSPECTING FOR HIGH-PRESSURE FUEL LEAKS.FUEL UNDER THIS AMOUNT OF PRESSURE CAN PENETRATE SKIN CAUSING PERSONAL INJURY OR DEATH. INSPECT FOR HIGH-PRESSURE FUEL LEAKS WITH A SHEET OF CARDBOARD. WEAR SAFETY
GOGGLES AND ADEQUATE PROTECTIVE CLOTHING WHEN SERVICING FUEL SYSTEM.Inspect the fuel system for contamination.Is the fuel contaminated?YesRepair as necessary in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 55.FUEL PRESSURE SENSOR CALIBRATIONTurn the ignition on.With the scan tool, read the Fuel Pressure Sensor volts.Does the scan tool display between 0.45 and 0.60 volts for the Fuel Pressure Sensor?YesGo To 6NoCheck the Fuel Pressure Sensor wiring and connectors for corrosion or poor terminal contact that could cause high resistance. Repair as necessary. If wiring
and connectors are o.k., replace the Fuel Pressure Sensor.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)6.ATTEMPT TO START ENGINEWith the scan tool, erase the ECM DTCs.Attempt to start the engine.Does the engine start and idle?YesGo To 7NoGo To 127.CHECKING FOR AIR IN FUEL SYSTEMWith the scan tool in Sensors, compare the Fuel Pressure Setpoint with the Actual Fuel Pressure readings.If there is air in the fuel system, the Actual Fuel Pressure will oscillate more than 100 psi above and/or below the Fuel Pressure Setpoint.Does Actual Fuel Pressure oscillate more than 100 psi above and/or below the Fuel Pressure Setpoint?YesRefer to the Service Information to purge air from the fuel system.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 88.FUEL PRESSURE SOLENOIDWith the scan tool, compare the Fuel Pressure Setpoint with the Actual Fuel Pressure.A sticking Fuel Pressure Solenoid is indicated by the Actual Fuel Pressure gradually dropping below the Fuel Pressure Setpoint then suddenly increasing (spiking) above
the Fuel Pressure Setpoint.Does the Actual Fuel Pressure gradually decrease then suddenly increase (spike) above the Fuel Pressure Setpoint?YesReplace the Fuel Pressure Solenoid in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 99.CHECKING FUEL DELIVERY SYSTEMRefer to the appropriate Service Information and refer to Diagnosis and Testing Fuel Delivery System table.The following is a list of problems that can cause fuel pressure to deviate from specification: restricted fuel filter or fuel lines, failed fuel pressure solenoid,
air in fuel system, failed fuel sending unit, contaminated fuel, faulty injector.Were there any problems with the Fuel Delivery System?YesRepair as necessary in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 1010.FUEL INJECTOR(S)An injector that sticks open can cause this DTC. A sticking injector will cause the engine to misfire and emit excessive black smoke from the exhaust system.Does the engine exhibit the symptoms described in the above note?YesUsing the Service Information, remove and inspect the Fuel Injectors for signs of damage or debris that may cause the injector to stick. Sticking injectors
may cause the combustion chamber to become black and oil soaked. Replace Injector(s) as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 1111.FUEL PRESSURE SOLENOIDTurn the ignition off.Replace the Fuel Pressure Solenoid in accordance with the Service Information.Turn the ignition on.With the scan tool, erase the ECM DTCs.Attempt to start and test drive the vehicle.With the scan tool, read the ECM DTCs.Does the ECM display this DTC?YesReplace the Fuel Pump in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoTest Complete.12.CHECKING FUEL DELIVERY SYSTEMRefer to the appropriate Service Information and refer to Diagnosis and Testing Fuel Delivery System table.The following is a list of problems that can cause fuel pressure to deviate from specification: restricted fuel filter or fuel lines, failed fuel pressure solenoid,
air in fuel system, failed fuel sending unit, contaminated fuel, faulty injector.Were there any problems with the Fuel Delivery System?YesRepair as necessary in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 1313.FUEL PRESSURE SOLENOIDTurn the ignition off.Replace the Fuel Pressure Solenoid in accordance with the Service Information.Turn the ignition on.With the scan tool, erase the ECM DTCs.Attempt to start and test drive the vehicle.With the scan tool, read the ECM DTCs.Does the ECM display this DTC?YesGo To 14NoTest Complete.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)14.FUEL QUANTITY SOLENOIDTurn the ignition off.Replace the Fuel Quantity Solenoid in accordance with the Service Information.Turn the ignition on.With the scan tool, erase the ECM DTCs.Attempt to start and test drive the vehicle.With the scan tool, read the ECM DTCs.Did this DTC set again?YesReplace the Fuel Pump in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoTest Complete.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)