P0088

4GR-FSE ENGINE CONTROL: SFI SYSTEM: P0088: Fuel Rail / System Pressure - Too High
P0088 - Fuel Rail / System Pressure - Too High

DESCRIPTION

The high-pressure fuel system consists of the spill valve, pump plunger, check valve, relief valve and fuel pressure sensor. The spill valve opens and closes the low-pressure fuel line (from the fuel tank), the pump plunger operated by the camshaft pressurizes fuel, the check valve mechanically opens and closes the high pressure fuel line (to the fuel delivery pipe), the relief valve prevents fuel pressure from becoming extremely high, and the fuel pressure sensor located on the fuel delivery pipe monitors fuel pressure.

The high-pressure side fuel pump is installed to the cylinder head cover (bank 1) and is driven by the cam located at the rear end of the exhaust camshaft.

When the plunger moves up and down due to camshaft rotation, it produces vacuum to suck fuel and pressurizes the fuel. This fuel then pushes the check valve open and flows into the fuel delivery pipe. The ECM opens and closes the spill valve to regulate the fuel pressure to the target fuel pressure of 4 to 13 MPa (40.8 to 132.6 kgf/cm2, 580 to 1886 psi). In order to obtain and maintain the target pressure, the ECM monitors the fuel pressure using the fuel pressure sensor and performs the feedback control.

If the internal fuel pressure of the fuel delivery pipe exceeds the standard pressure of 15.3 MPa (156.0 kgf/cm2, 2219 psi), the fuel relief valve installed on the gateway of the fuel delivery pipe discharges the fuel pressure and then returns the fuel back to the fuel tank.





Text in Illustration









MONITOR DESCRIPTION

If the fuel pressure does not decrease even after the ECM commands the high-pressure fuel pump to open the spill control valve, a DTC is output.

If there is minimal difference between the fuel pressure before and after the fuel relief valve operates, a DTC is output.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





CONFIRMATION DRIVING PATTERN

- Connect the Techstream to the DLC3.

- Turn the engine switch on (IG) and turn the Techstream on.

- Record the Freeze Frame Data.

- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) DTC Check / Clear.

- Turn the engine switch off.

- Turn the engine switch on (IG) and turn the Techstream on.

- Based on engine rpm, engine load and other freeze frame data stored in the ECM, reproduce the conditions present when the DTC was stored.

- Enter the following menus: Powertrain / Engine / Utility / All Readiness.

- Input the DTC: P0088.

- Check the DTC judgment result.





HINT
If the judgment result shows ABNORMAL, the system has a malfunction.

- If the test result is UNKNOWN, enter the following menus: Powertrain / Engine / Trouble Code / Pending.

- Read Pending DTCs.

HINT
If a pending DTC is output, the system is malfunctioning.

- If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear.

HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.
WIRING DIAGRAM





INSPECTION PROCEDURE

HINT
Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0088)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Enter the following menus: Powertrain / Engine / Trouble Codes.

(d) Read the DTCs.

Result:





HINT
If any DTCs other than P0088 are output, troubleshoot those DTCs first.

B -- GO TO DTC CHART SFI System
A -- Continue to next step.

2. CHECK FUEL PRESSURE SENSOR

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Enter the following menus: Powertrain / Engine / Data List / Fuel Press.

(d) Check that the fuel pressure fluctuates when the engine is raced.

OK:

Fuel pressure fluctuates.

NG -- REPLACE FUEL PRESSURE SENSOR
OK -- Continue to next step.

3. REPLACE FUEL PUMP FOR HIGH PRESSURE

(a) Replace the fuel pump for high pressure Removal.

NEXT -- Continue to next step.

4. CHECK IF DTC OUTPUT RECURS (SEE IF DTC P088 IS OUTPUT AGAIN)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Clear the DTCs.

(d) Start the engine.

(e) Enter the following menus: Powertrain / Engine / Trouble Codes.

(f) Read the DTCs.

Result:





B -- END
A -- Continue to next step.

5. INSPECT FUEL RELIEF VALVE

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Enter the following menus: Powertrain / Engine / Data List / Fuel Press.

(d) Start the engine.

(e) Check the fuel pressure.

Result:





B -- REPLACE FUEL RELIEF VALVE

A -- REPLACE ECM Removal