Fuel pressure monitoring is used to detect the troubles and the fuel leakage in high pressure system.

The ECM determines the rail pressure value as a function of the engine’s operating conditions and controls the fuel pressure regulator to ensure that the rail pressure reaches the required value.

Fuel pressure in the fuel line including the pumps and injector are continuously monitored during engine runing.

If the rail pressure is excessive, the fuel pressure regulator opens and a portion of the fuel is returned from the rail to the fuel tank via a collector line. If the rail pressure is too low, the fuel pressure regulator closes.

The fuel pressure regulator closes. the fuel pressure regulator is installed in the tail end of high pressure accumulator.

In case of the insufficient fuel supply in the fuel line, the engine symptoms will occur a shut down and a starting impossible.

If the fuel pressure monitoring in engine fuel pressure line generates threshold value, the ECM judged this as a fault and DTC is set.

Fig 1) Normal value with fuel pressure and pressure regulator at idle.

Fig 2) Normal value with fuel pressure and engine speed while accelerating and decelerating.

Is the Current data displayed correctly ?

▶ Fault is intermittent caused by poor contact in the sensor’s and/or ECM’s connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

▶ Go to "W/Harness Inspection" procedure.

3.

Has a problem been found?

Repair as necessary and go to "Verification of Vehicle Repair" procedure.

Go to " Component Inspection " procedure.

1.

Check Rail pressure.

(1)

Ignition "ON" & Engine "ON".

(2)

Ignition "OFF" then Igintion "ON" before Main relay OFF.

(3)

Monitor signal waveform or graph function of current data by connecting scantool at terminal 2 of Rail preussure regulator.

note

1.

If Main relay OFF, Monitoring current data is impossible. Because Sensor power is cut and communication between scantool and ECM is off.

2.

This test should be done without any leakage from injector nozzle, return line and high pressure line.

3.

Time to pressurize upto 250bar is required as shortly as possible after starting but the time to release the pressure to 100 bar after ignition off is required as quickly as passble. However, time to release the pressure from 100bar to 0bar is required as slowly as possible. Refer to picture1 and 2 as below.

Voltage	Pressure
Voltage from rail pressure sensor at idle is required to keep up with 1.2V ~ 1.4V. Then, the voltage will be drop to 0.7V at the point of Key off. Finally Voltage is getting slowly down	Pressure detected by Rail pressure sensor is required to keep up with 250bar at idle. Then, Pressure will be drop rapidly upto 100bar at the point of key off. Finally, Pressure is getting slowly down

(4)

Is the rail pressure data displayed correctly ?

▶ Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

▶ Perform Rail Pressure Sensor & Rail Pressure regulator Inspection procedure. For more detail information, refer to DTC P0192,P0193 and P0190 for Rail Pressure sensor and DTC P1182,P1183 and P1184 for Rail Pressure regulator troubleshooting procedure.

Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

After a repair, it is essential to verify that the fault has been corrected.

3.

Are any DTCs present ?

Go to the applicable troubleshooting procedure.

System is performing to specification at this time.