Code No. P0088: Common Rail High Pressure Malfunction

OPERATION

5 V power is supplied from the engine-ECU (terminal No. 81) to the rail pressure sensor (terminal No. 1).
The rail pressure sensor (terminal No. 3) is earthed to the engine-ECU (terminal No. 76).
Sensor signals are input from the rail pressure sensor (terminal No. 2) to the engine-ECU (terminal No. 56).

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).

PROBABLE CAUSES

Failed suction control valve
Failed rail pressure sensor
Failed engine-ECU

DIAGNOSIS PROCEDURE

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

Q. Is any other diagnosis code than P0088 output?

	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 supply pump assembly. After replacing the supply pump, learn the supply pump (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

STEP 3. Connector check: C-105 engine-ECU connector and A-47 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 the C-105 (terminal No. 17) engine-ECU connector and A-47 (terminal No. 1) suction control valve connector.

Check output 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 the C-105 (terminal No. 37) engine-ECU connector and A-47 (terminal No. 2) suction control valve connector.

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 A-47 suction control valve (Using an oscilloscope).

Engine: Idling
Connect the oscilloscope special patterns pickup to engine-ECU terminal No. 37 and earth.

OK: Output waveform timings of both sensors are the same as the check procedure (Refer to ) using an oscilloscope.

Q. Is the check result normal?

Go to Step 7 .

Replace the engine-ECU then replace the common rail assembly and fuel injection tubes. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - How to Perform Chassis Number Writing

). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns

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 trouble symptom persist?

	Replace the supply pump assembly. After replacing the supply pump, learn the supply pump (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

	The check is end.