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 LowDTC P0088: Fuel Rail Pressure (FRP) Too High
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
FRP Sensor 5-Volt Reference | P0117, P0522, P0652, P0700 | P0087, P0191, P0192, P0700 | P0193 | P0533, P0653 | -- |
FRP Sensor Signal | P0192 | P0191 | P0193 | P0193 | -- |
Fuel Pressure Regulator Solenoid Supply Voltage | 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 20 MPa (2,900 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
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. The control module records the operating conditions at the time the diagnostic fails and stores this information in the Freeze Frame/Failure Records. The ECM will limit fuel injection.
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
P0087
| • | Gasoline contamination of the fuel may cause this DTC to 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 effect the fuel system components. |
| • | If the fuel pressure 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 . |
| • | A sticking FRP regulator may cause this DTC to set. |
| • | 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
| • | Driveability concerns may not occur with this DTC present. |
| • | If the fuel system pressure is actually too high, a fuel knock and smoke condition will exist. |
| • | A sticking FRP regulator may cause this DTC to set. |
Reference Information
Schematic Reference
Electrical Information Reference
| • | Circuit Testing |
| • | Wiring Repairs |
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Special Tools Required
CH-48027 Digital Pressure Gage
Circuit/System Verification
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. Inspect the fuel supply lines for damage between the fuel tank and the fuel injection pump.
Circuit/System Testing
P0087
- If DTC P0090, P0168 or P0191 is also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Ignition ON for 90 seconds, verify the scan tool FRP Regulator Command parameter is less than 20 percent.
- Attempt to start the engine.
- Install the CH-48027 to the fuel rail service port and slowly increase the engine speed until reaching wide open throttle (WOT).
- 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.
- 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.
- 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.
| ⇒ | If greater than the specified range, replace the ECM. |
Important: Ensure that the transmission is in Park or Neutral with the parking brake set.
| ⇒ | If the engine does not start, refer to Engine Cranks But Does Not Run . |
| ⇒ | If more than 5 inches Hg of vacuum was present during engine speed increase, replace the fuel filter and inspect for fuel system restrictions. |
| ⇒ | If the Actual Fuel Rail Pressure is less than 145 MPa (21,030 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 .
| ⇒ | 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. |
| ⇒ | 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
- 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.
- 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.
- Change 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 2 MPa (290 psi) of each other.
- Test the fuel pressure regulator (FPR) solenoid control circuit and the FPR solenoid supply voltage circuit for high resistance.
| ⇒ | If the pressure difference between the actual and desired pressure are more than 2 MPa (290 psi), replace the fuel pressure regulator. |
| ⇒ | If all circuits test normal, refer to Diagnostic Aids |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
