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DTC P0087 or P0088 - LNP or LNQ

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 P0087 00: Fuel Rail Low Pressure

DTC P0088 00: Fuel Rail High Pressure

Circuit/System Description

The engine control module (ECM) uses commanded fuel pump flow to determine a desired fuel rail pressure. The ECM monitors fuel rail pressure with the fuel rail pressure sensor. The Fuel Pressure Regulator Solenoid 1 is used to control the fuel pressure at the fuel rail. The Fuel Pressure Regulator Solenoid 1 is pulse width modulated (PWM). The ECM supplies the voltage directly to the Fuel Pressure Regulator Solenoid 1. The ECM controls the solenoid by grounding the control circuit with a solid state device called a driver.

Conditions for Running the DTC
    • The engine is running.
    • The DTCs runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0087 00

The ECM detects that the fuel rail pressure exceeds the minimum threshold.

P0088 00

The ECM detects that the fuel rail pressure exceeds the maximum positive deviation of rail pressure.

Action Taken When the DTC Sets

DTCs P0087 00, and P0088 00 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P0087 00, and P0088 00 are Type A DTCs.

Diagnostic Aids
    • A restricted fuel supply line, a leakage in the high pressure section, too much or too little fuel in the low pressure line may cause DTCs to set. When ambient temperatures are below 0°C (32°F), the fuel tank pickup screen may be iced over from water in the fuel tank.
    • High resistance in either circuit of the fuel pressure regulator will cause a DTC to set.
    • There are no driveability concerns associated with the fuel rail pressure regulator unless a DTC is present. One of the causes of these DTCs is a sticking fuel rail pressure regulator.
    • If the fuel system pressure is actually too high, a fuel knock and smoke condition will exist.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

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

Special Tools

EN 34730-1A Fuel Pressure Gauge

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification
  1. Ignition ON, observe the DTC information with a scan tool. Verify that no other DTCs are set.
    2. ⇒If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
  2. Engine running, observe the scan tool DTC information parameter. DTCs P0087 00, or P0088 00 should not set.
  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
  1. Ignition ON, command the fuel pump ON and OFF with a scan tool. Verify the fuel pump turns ON.
    2. ⇒If the fuel pump does not turn ON, refer to Fuel Pump Electrical Circuit Diagnosis for further diagnosis.
  2. Ignition OFF, install the EN 34730-1A fuel pressure gauge .
  3. Ignition ON, verify the fuel pressure is between 414-550 kPa (60-80 PSI).
    4. ⇒If not within the specified range, refer to Fuel System Diagnosis for further diagnosis.
  4. Ignition OFF, disconnect the harness connector at the Q18 Fuel Pressure Regulator.
  5. Ignition ON, verify a test lamp illuminates between the ignition voltage circuit terminal 2 and ground.
    6. ⇒If the test lamp does not illuminate, repair the ignition voltage circuit for a short to ground or an open/high resistance.
  6. Ignition ON, test for 6.5-11 V between the control circuit terminal 1 and ground.
    7. ⇒If less than the specified range, test the control circuit for an open or a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
    ⇒If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
  7. Inspect and repair one of the following conditions:

    8. Low Pressure

    • A fuel system leak
    • Restricted fuel filter
    • Injection nozzle stuck in open position
    • Leakage in the fuel rail pressure regulator
    • Worn fuel injection pump

    High Pressure

    • Restricted fuel return
    • Fuel injection pump stuck open
    • Fuel rail pressure regulator stuck closed
    • Restricted fuel injector
  8. If all circuits test normal, replace the Q18 Fuel Pressure Regulator.

Component Testing

Static Test

  1. Ignition OFF, disconnect the harness connector at the Q18 Fuel Pressure Regulator.
  2. Test for 6-7 Ω between the control terminal 1 and the ignition voltage terminal 2.
    3. ⇒If not within the specified range, replace the Q18 Fuel Pressure Regulator.
  3. Test for infinite resistance between each terminal and the Q18 Fuel Pressure Regulator housing.
    4. ⇒If not the specified value, replace the Q18 Fuel Pressure Regulator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Fuel Injection Pump Replacement
    •  Fuel Injector Replacement
    • Control Module References for ECM replacement, programming and setup
   


© Copyright Chevrolet. All rights reserved
   


© Copyright Chevrolet. All rights reserved