Code No. P1272: Pressure Limiter Malfunction


OPERATION



  • Refer to Code No. P0191: Rail Pressure Sensor Range/Performance Problem
  • Refer to Code No. P0003: Suction Control Valve Open

FUNCTION



  • The engine-ECU controls the fuel discharge rate using the suction control valve.
  • The engine-ECU monitors the signals input from the rail pressure sensor.
  • The engine-ECU checks whether the pressure limiter valve is open, based on changes in the signals input from the rail pressure sensor (rapid drop of pressure after it goes extremely high).

TROUBLE JUDGMENT


Check Conditions
  • Battery positive voltage is 8 - 16 V.
  • 2 seconds later after the ignition switch has been in "ON" position or the engine has started up.
  • Engine speed is 600 r/min or more.
  • Rail pressure sensor is normal.
Judgment Criterion
  • After a pressure higher than the pressure of the pressure limiter opening valve is detected, fuel leakage diagnosis (supply pump discharge rate excessive) is detected within the predetermined time.

FAIL-SAFE AND BACKUP FUNCTION



  • The EGR control is stopped (fully closed).
  • The DPF regeneration is prohibited.
  • The throttle valve is opened (Electrical discontinuity).
  • The AS&G control is prohibited.

PROBABLE CAUSES



  • Failed suction control valve
  • Failed fuel system
  • Open/short circuit in suction control valve circuit or loose connector contact
  • Failed common rail assembly
  • Failed engine-ECU

DIAGNOSIS PROCEDURE
note This diagnosis code is outputted for an air penetration in the fuel line of the supply pump due to lack of fuel. Therefore, bleed air from the fuel line after the fuel supply, and delete the diagnosis code through M.U.T.-III. Repeat the cycle turning on the ignition switch and leaving it for 20 seconds to bleed air from the fuel line.

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

Q. Is the check result normal?
Inspection chart for diagnosis codes (Refer to ).
Go to Step 2 .

STEP 2. Check the fuel filter contamination

Q. Is the check result normal?
Go to Step 3 .
Replace the fuel filter then replace the common rail assembly and fuel injection tubes.

STEP 3. Release the air from the fuel line.

  • Repeat, more than 3 times, the cycle turning on the ignition switch and leaving it for more than 20 seconds. Operate the fuel pump in the fuel tank. Check there is no air at all in the fuel pipe.

Q. Does the trouble symptom persist?
Replace the common rail assembly and common tubes.
Go to Step 4 .

STEP 4. Check suction control valve itself

  • Check suction control valve itself (Refer to ).

Q. Is the check result normal?
Go to Step 5 .
Replace the suction control valve. After replacing the suction control valve, learn the supply pump (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

STEP 5. Connector check: B-09 engine-ECU connector and B-07 suction control valve connector.

Q. Are the check results normal?
Go to Step 6 .
Repair or replace the connector then replace the common rail assembly and fuel injection tubes.

STEP 6. Check harness between B-09 (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 output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 7 .
Repair the damaged harness wire then replace the common rail assembly and common tubes.

STEP 7. 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 8 .
Repair the damaged harness wire then replace the common rail assembly and fuel injection tubes.

STEP 8. Perform output wave pattern measurement at B-10 engine-ECU (Using an oscilloscope).

  • Engine: Idling
  • Connect the oscilloscope special patterns pickup to engine-ECU terminal No. 131 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 9 .
Replace the engine-ECU.

STEP 9. Replace the common rail assembly and fuel injection tubes.

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

Q. Does the 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.