For 1990-2009 cars

### 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 Descriptor

DTC P0087 51: Fuel Rail Pressure Too Low
DTC P0087 53: Fuel Rail Pressure Too Low
DTC P0087 55: Fuel Rail Pressure Too Low
DTC P0088 51: Fuel Rail Pressure Too High
DTC P0088 52: Fuel Rail Pressure Too High
DTC P0088 53: Fuel Rail Pressure Too High
DTC P0088 54: Fuel Rail Pressure Too High
DTC P0088 57: Fuel Rail Pressure Too High
DTC P0088 58: Fuel Rail Pressure Too High
DTC P0088 59: Fuel Rail Pressure Too High
DTC P0088 5A: Fuel Rail Pressure Too High
DTC P0088 5D: Fuel Rail Pressure Too High

### 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 engine control module (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 51, P0087 53 and P0087 55

The ECM detects that the rail pressure is below the minimum threshold.

#### P0088 51, P0088 52, P0088 58, P0088 59, P0088 5A and P0088 5D

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

#### P0088 53

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

#### P0088 54, P0088 57

The ECM detects that the rail pressure exceeds the maximum rail pressure.

### Action Taken When the DTC Sets

DTCs P0087 51, P0087 53, P0087 55, P0088 51, P0088 52, P0088 58, P0088 59, P0088 5A, P0088 5D, P0088 53, P0088 54, and P0088 57 are Type A DTCs.

### Conditions for Clearing the DTC

DTCs P0087 51, P0087 53, P0087 55, P0088 51, P0088 52, P0088 58, P0088 59, P0088 5A, P0088 5D, P0088 53, P0088 54, and P0088 57 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 1 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

DW100-010 Fuel Pressure Gage

### Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify that no other DTCs are set.

⇒ | 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, or P0088 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.

⇒ | If the fuel pump does not turn ON, refer to Fuel Pump Electrical Circuit Diagnosis for further diagnosis.

2. Ignition OFF, install the DW100-010 , refer to Link.
3. Ignition ON, verify the fuel pressure is between 414-483 kPa (60-70 PSI).

⇒ | If not within the specified range, refer to Fuel System Diagnosis for further diagnosis.

4. Ignition OFF, disconnect the harness connector at the fuel pressure regulator solenoid 1.
5. Ignition ON, verify a test lamp illuminates between the ignition voltage circuit terminal 1 and ground.

⇒ | 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 3-4 V between the control circuit terminal 2 and ground.

⇒ | If less than the specified range, test the control circuit for an open or a short to ground. If circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the control circuit for a short to voltage. If circuit tests normal, replace the K20 Engine Control Module (ECM).

7. Inspect and repair one of the following conditions:

#### 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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Link

• | Fuel Injection Pump Replacement

• | Fuel Injector Replacement

• | Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming