P0088

DTC P0087, P0088, or P0089

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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 reference ground circuit. The ECM receives a varying signal voltage on the signal circuit.

High pressure fuel is regulated by the fuel rail pressure (FRP) regulator, which is a part of the high pressure fuel pump. The FRP regulator is a solenoid valve. The ECM provides battery voltage on the FRP regulator hi circuit and ground on the FRP regulator low circuit. Both circuits are controlled through output drivers within the ECM. When deactivated, both drivers are disabled. When activated, the FRP regulator low circuit driver connects the low circuit to ground and the FRP regulator hi circuit driver pulse-width modulates (PWM) the hi 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 FRP regulator 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 FRP regulator. 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, P0192, P0193 are not set.
* The ignition 1 signal parameter is less than 18.1 volts.
* The relative injected fuel mass is between 5.016-300 percent.
* The deceleration fuel cut-off (DFCO) is inactive.
* The engine speed is more than 25 RPM.
* The engine start temperature is more than -48°C (-54.4°F)
* DTCs P0087, P0088, and P0089 run continuously when the above conditions are met for 5 seconds.

Conditions for Setting the DTC

P0087

The actual fuel pressure is more than 1500 kPa below the desired fuel pressure.

P0088

The actual fuel pressure is more than 2000 kPa above the desired fuel pressure.

P0089

The fuel pressure adjustment is more than +3,000 kPa or less than -3,000 kPa.

DTCs P0087, P0088, and P0089 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 pressure sensor may set these DTCs.
* Faulty fuel injectors may set DTC P0089.

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. Component Tests and General Diagnostics
2. Remove the high pressure pump assembly and visually inspect the lobes on the camshaft for wear.

• If the lobes are normal, replace the mechanical fuel pump assembly.

• If the lobes are worn, replace the camshaft.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement
* Fuel Pump Module Replacement
* High Pressure Fuel Pump Replacement