Code No. P1274: Supply Pump Protection


FUNCTION



  • The engine-ECU monitors the signals input from the rail pressure sensor.
  • Based on these input signals, the engine-ECU checks whether the fuel pressure in the common rail is abnormal.

TROUBLE JUDGMENT


Check Conditions
  • Engine is running
  • Rail pressure sensor is normal
Judgment Criterion
  • For 1 second, the rail pressure stays in the critical pressure range in which the supply pump in burned out.

FAIL-SAFE AND BACKUP FUNCTION



  • The rail pressure is controlled in the range between 50 and 60 MPa.
  • The fuel injection amount is restricted (Output restriction).
  • The open angle of the accelerator pedal is restricted.
  • 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 supply pump
  • Failed rail pressure sensor
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

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

Q. Is any other diagnosis code than P1274 output?
Inspection chart for diagnosis codes (Refer to ).
Go to Step 2.

STEP 2. 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 3.
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 3. Replace the supply pump assembly.

  • After the supply pump assembly, learn the supply pump (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns <4N1> ).
  • After learning the supply pump assembly, re-check the trouble symptoms.

Q. Does trouble symptom persist?
Go to Step 4.
The check is end.

STEP 4. 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 engine-ECU.
The check is end.