Code No. P0088: Common Rail High Pressure Malfunction

OPERATION

Refer to Code No. P0003: Suction Control Valve Open

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 JUDGEMENT

Check Conditions

Rail pressure sensor is normal.
Battery positive voltage is 8 - 16 V.

Judgement 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 60 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.

PROBABLE CAUSES

Failed suction control valve
Failed engine-ECU

DIAGNOSIS 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. Check of open circuit, short to earth, and damage in SCV+ line between engine-ECU connector and suction control valve connector.

Q. Is the check result normal?

	Go to Step 4.

	Repair the connector(s) or wiring harness.

STEP 4. Check of open circuit, short to earth, and damage in SCV- line between engine-ECU connector and suction control valve connector.

Q. Is the check result normal?

	Go to Step 5.

	Repair the connector(s) or wiring harness.

STEP 5. Perform output wave pattern measurement at suction control valve connector (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 suction control valve connector (SCV+ line) and body 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 6.

	Replace the suction control valve.

STEP 6. 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.