Code No. P1272: Pressure Limiter Malfunction




OPERATION




FUNCTION




TROUBLE JUDGMENT


Check Conditions
Judgment Criterion

FAIL-SAFE AND BACKUP FUNCTION




PROBABLE CAUSES




DIAGNOSIS PROCEDURE


note This diagnosis code is set 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 any other diagnosis code than P1272 output?

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



  • Suction control valve connector check.
  • Check suction control valve itself (Refer to ).

Q. Is the check result normal?

Go to Step 5.
Repair or replace the connector, or 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 <4N1> ).

STEP 5. Check harness between engine-ECU connector terminal SCV+ and suction control valve connector terminal.



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

Q. Is the check result normal?

Go to Step 6.
Repair or replace the connector, or repair the damaged harness wire then replace the common rail assembly and common tubes.

STEP 6. Check harness between engine-ECU connector terminal SCV- and suction control valve connector terminal.



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

Q. Is the check result normal?

Go to Step 7.
Repair or replace the connector, or repair the damaged harness wire then replace the common rail assembly and fuel injection tubes.

STEP 7. Perform output wave pattern measurement at engine-ECU (Using an oscilloscope).



  • Engine: Idling
  • Connect the oscilloscope special patterns pickup to engine-ECU terminal SCV+ 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 8.
Replace the engine-ECU.

STEP 8. 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 <4N1> ).
The check is end.