Code No. P0088: Common Rail High Pressure Malfunction


OPERATION



FUNCTION



  • The engine-ECU monitors the signals input from the rail pressure sensor.
  • Based on The input signals, the engine-ECU checks whether the fuel pressure in the common rail exceeds the maximum withstand pressure of the system.

TROUBLE JUDGMENT


Check Conditions
  • Rail pressure sensor is normal.
  • Battery positive voltage is 8 - 16 V.
Judgment Criterion
  • The rail pressure exceeds the threshold value of an abnormal high pressure for 3 seconds (continuous or accumulated).

FAIL-SAFE AND BACKUP FUNCTION



  • The throttle valve is closed (Fixed opening degree).
  • The rail pressure is controlled in the range between 50 and 100 MPa.
  • The DPF regeneration is prohibited.
  • The fuel injection amount is restricted (Output restriction).
  • The EGR control is stopped (fully closed).
  • The open angle of the accelerator pedal is restricted.
  • The AS&G control is prohibited.

PROBABLE CAUSES



  • Failed suction control valve
  • Failed engine-ECU

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III diagnosis code

Q. Is any other diagnosis code than P0088 set?
Inspection chart for diagnosis codes (Refer to ).
Go to Step 2 .

STEP 2. Check suction control valve itself.

  • Check suction control valve itself (Refer to ).

Q. Is the check result normal?
Go to Step 3 .
Replace the suction control valve.

STEP 3. Connector check: B-10 engine-ECU connector and B-07 suction control valve connector.

Q. Are the check results normal?
Go to Step 4 .
Repair or replace the connector then replace the common rail assembly and fuel injection tubes.

STEP 4. Check harness between B-10 (terminal No. 131) engine-ECU connector and B-07 (terminal No. 1) suction control valve connector.
note Before checking harness, check intermediate connector A-16, and repair if necessary.

  • Check power supply line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 5 .
Repair the damaged harness wire then replace the common rail assembly and fuel injection tubes.

STEP 5. Check harness between B-10 (terminal No. 146) engine-ECU connector and B-07 (terminal No. 2) suction control valve connector.
note Before checking harness, check intermediate connector A-16, and repair if necessary.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 6 .
Repair the damaged harness wire then replace the common rail assembly and fuel injection tubes.

STEP 6. Perform output wave pattern measurement at B-07 suction control valve (Using an oscilloscope).

  • Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
  • Engine: Idling
  • Connect the oscilloscope special patterns pickup to terminal No. 1 and earth.
OK: The waveform should show a pattern similar to the illustration of inspection procedure using an oscilloscope (Refer to ).

Q. Is the check result normal?
Go to Step 7 .
Replace the suction control valve.

STEP 7. Replace the common rail assembly and fuel injection tubes.

  • After replacing the common rail assembly and fuel injection tubes, re-check the trouble symptoms

Q. Does the trouble symptom persist?
Replace the engine-ECU.
The check is end.