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 Descriptors

DTC P0087: Fuel Rail Pressure (FRP) Too Low
DTC P0088: Fuel Rail Pressure (FRP) Too High
DTC P0089: Fuel Pressure Regulator Performance

### Circuit/System Description

The fuel rail pressure sensor detects fuel pressure within the fuel rail. The engine control module (ECM) provides a 5-volt reference voltage on the 5-volt reference circuit and ground on the low reference circuit. The ECM receives a varying signal voltage on the signal circuit.

High pressure fuel is regulated by the high pressure fuel pump actuator, which is a part of the high pressure fuel pump. The actuator regulator is a solenoid valve. The ECM provides battery voltage on the actuator high control circuit and ground on the actuator low control circuit. Both circuits are controlled through output drivers within the ECM. When deactivated, both drivers are disabled. When activated, the actuator low control circuit driver connects the low control circuit to ground and the actuator high control circuit driver pulse-width modulates (PWM) the high control circuit.

The high pressure mechanical fuel pump is driven by three lobes on the camshaft. The ECM uses the camshaft and crankshaft position sensor inputs to synchronize the high pressure fuel pump actuator with the position of each of these camshaft lobes. The ECM regulates fuel pressure by adjusting the portion of each pump stroke that provides fuel to the rail.

The ECM creates a feedback loop between the pressure sensor and the high pressure fuel pump actuator. If the difference between expected and actual inputs exceeds a calibrated value, or if the amount of correction exceeds a calibrated value, a DTC sets.

### Conditions for Running the DTC

• | DTCs P0090, P0091, P0092, P0191, P0192, P0193 are not set.

• | The ignition 1 signal parameter is less than 18.1 volts.

• | The relative injected fuel mass is between 5.016-500 percent.

• | The deceleration fuel cut-off (DFCO) is inactive.

• | The engine speed is greater than 25 RPM.

• | The engine start temperature is greater than -48°C (-54.4°F)

• | The DTCs run continuously when the above conditions are met for 2 seconds.

### Conditions for Setting the DTC

#### P0087

The actual fuel pressure is 1500 kPa (218 psi) less than the desired fuel pressure.

#### P0088

The actual fuel pressure is 2000 kPa (290 psi) greater than the desired fuel pressure.

#### P0089

• | The fuel pressure adjustment is greater than +2,500 kPa (+363 psi) or less than -2,500 kPa (-363 psi).

• | The DTCs set when the above conditions are met for 4 seconds.

### Action Taken When the DTC Sets

• | DTCs P0087, P0088, and P0089 are Type A DTCs.

• | A message center or an indicator displays Reduced Engine Power when DTC P0087 sets.

### Conditions for Clearing the DTC

DTCs P0087, P0088, and P0089 are Type A DTCs.

### Diagnostic Aids

• | A skewed fuel rail fuel pressure sensor may set these DTCs.

• | Faulty fuel injectors may set DTCs P0087 or P0089.

### 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

### Circuit/System Verification

1. If any other DTCs are set, perform those diagnostics first.
2. Operate the vehicle within the parameters described in Conditions for Running and Conditions for Setting. The DTC should not set this ignition.

⇒ | If the DTC sets this ignition, proceed with Circuit/System Testing.

### Circuit/System Testing

Important: Circuit/System Verification must be performed first or misdiagnosis may result.

1. Verify the correct low side fuel system pressure. Refer to Fuel System Diagnosis.
2. Remove the high pressure fuel pump assembly and visually inspect the lobes on the camshaft for wear.

⇒ | If the lobes are normal, replace the high pressure fuel pump.

⇒ | If the lobes are worn, replace the camshaft.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement

• | Fuel Pump Module Replacement

• | High Pressure Fuel Pump Replacement

• | Intake Camshaft and Valve Lifter Replacement