GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0087 or P0088

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: Fuel Rail Pressure (FRP) Too Low

DTC P0088: Fuel Rail Pressure (FRP) Too High

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

FRP Sensor 5-Volt Reference

P0117, P0462, P0522, P0652, P0700, P2454

P0087, P0191, P0192, P0700

P0193

P0533, P0653

FRP Sensor Signal

P0192

P0191

P0193

P0193

Fuel Pressure Regulator Solenoid Supply Voltage

P0088, P0090

P0088

P0090

P0087, P0191, P2510

Fuel Pressure Regulator Solenoid Control

P0088, P0090

P0088

P0090

P0090

Circuit/System Description

The fuel injection pump supplies high pressure fuel to the fuel injection rails, and then to the fuel injectors through high pressure pipes. The fuel rail pressure (FRP) sensor is a three wire sensor mounted in the right fuel injection rail. The FRP sensor uses a 5-volt reference circuit , a signal circuit, and a low reference circuit to monitor fuel rail pressure. This information is sent to the engine control module (ECM) to assist in the fueling of the engine.

Conditions for Running the DTC

P0087

    • DTCs P0090, P0192, P0193 are not set.
    • The engine is running.

P0088

    • DTCs P0087, P0192, P0193 are not set.
    • The engine is running.

Conditions for Setting the DTC

P0087

    • The actual FRP is more than 15 MPa (2,176 psi) below the desired FRP.
        OR
    • The actual FRP is less than 22.5 MPa (3,263 psi).

P0088

    • The actual FRP is more than 20 MPa (2,900 psi) above the desired FRP.
        OR
    • The actual FRP is more than 189 MPa (27,412 psi).

Action Taken When the DTC Sets
    • DTCs P0087 and P0088 are Type A DTCs.
    • 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

DTCs P0087 and P0088 are Type A DTCs.

Diagnostic Aids

P0087

       Important: If the Change Fuel Filter Warning light is ON with DTC P0087, inspect the fuse filter for a restriction or contamination.

    • Water or gasoline contamination of the fuel may cause this DTC to intermittently set. Refer to 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.
    • 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.
    • If the fuel pressure relief valve is not torqued correctly, the valve will leak fuel into the fuel return system causing this DTC to set. The fuel pressure relief valve uses a bite type seal, and proper torque is essential for valve to rail sealing. Refer to Fastener Tightening Specifications.
    • 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

    • This DTC will set if the electric fuel prime pump runs continuously during engine operation (van only).
    • If the fuel system pressure is actually too high, a fuel knock will exist.
    • A sticking FRP regulator may cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

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

CH-48027 Digital Pressure Gage

Circuit/System Verification
  1. With engine running, observe the Actual Fuel Rail Pressure parameter with a scan tool. A normal reading would be approximately 40 MPa (5,802 psi) with the engine cold, and 30 MPa (4,351 psi) at operating temperature.
  2. Engine running, observe the DTC information with a scan tool. DTCs P0087 or P0088 should not set.
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

Important: 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. If DTC P0090, P0168 or P0191 is also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
  2. Ignition ON for 90 seconds, verify the scan tool FRP Regulator Command parameter is less than 20 percent.
    3. ⇒If greater than the specified range, replace the ECM.
  3. Attempt to start the engine.
    4. ⇒If the engine does not start, refer to Engine Cranks But Does Not Run.
  4. Install the CH-48027 to the fuel rail service port and slowly increase the engine speed until reaching wide open throttle (WOT). The value should be between 1-4 inches Hg vacuum.
    5. ⇒If more than the specified value, inspect for restricted fuel filter or damaged supply lines.
    ⇒If no restriction was found, test for high fuel return flow. Refer to Fuel System Diagnosis - High Pressure Side.
  5. With the engine idling or at an idle, command the fuel pressure control to 180 MPa (26,106 psi) with a scan tool. Observe the Actual Fuel Rail Pressure parameter. The actual fuel pressure should be the same as the commanded pressure.
    6. ⇒If the Actual Fuel Rail Pressure is less than 165 MPa (23,931 psi), refer to Fuel System Diagnosis - High Pressure Side.

    Important: If the fuel temperature is near 121°C (250°F) during the duplication of the complaint, or in the Failure Records for this DTC, inspect for a restriction in the fuel cooler air flow or the fuel heater always ON. Refer to Fuel Heater Always On.

  6. Operate the vehicle within the conditions for which the customer complaint occurs while observing the CH-48027 . You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records.
    7. ⇒If the vacuum was more than 12 inches Hg of vacuum at any time in the operating range, inspect for kinked or restricted fuel supply lines.
  7. Operate the vehicle within the conditions for which the customer complaint occurred. Observe the Actual fuel Rail Pressure and Desired Fuel rail Pressure parameters with a scan tool. Fuel pressures should be the same for both parameters.
    8. ⇒If the Actual Fuel Rail Pressure is less than the Desired Fuel Rail Pressure, refer to Fuel System Diagnosis - High Pressure Side.
    ⇒If fuel system tests normal, refer to Diagnostic Aids.

P0088

  1. Start the engine and operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
  2. Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 30 MPa (4,352 psi) with the engine idling at operating temperature.
  3. Command the fuel pressure with a scan tool, incrementing through the entire fuel pressure range. The fuel pressure should increment and stabilize through the entire fuel pressure range with actual and desired fuel pressure within 5 MPa (725 psi) of each other.
    4. ⇒If the pressure difference between the actual and desired pressure are more than 5 MPa (725 psi), test the solenoid supply voltage circuit and the solenoid control circuit for high resistance or a short to ground. If the circuits test normal, replace the FRP regulator.
    ⇒If the pressure difference between the actual and desired pressure is less than 5 MPa (725 psi), refer to Diagnostic Aids.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Pressure Regulator Replacement