Code No. P244A: DPF Differential Pressure Too Low


FUNCTION



  • The engine-ECU monitors the difference between exhaust gas pressures at the inlet and outlet of the DPF by using the exhaust differential pressure sensor.
  • If the difference is abnormally low, the engine-ECU will determine that the DPF is melted down or missing.

TROUBLE JUDGMENT


Check Condition
  • The engine is stable (various factors such as engine speed, fuel injection amount, intake air flow, exhaust gas temperate are within a predetermined range).
  • Exhaust gas flow exceeds a predetermined value.
  • Estimated PM accumulated deposit, which is calculated from a current estimated engine exhaust PM amount, exceeds a predetermined value.
  • The distance travelled since the last DPF regeneration exceeds a predetermined value.
Judgement Criterion
  • The difference between exhaust gas pressures at the inlet and outlet of the DPF remains smaller than the pressure difference which is estimated during no PM accumulation in the DPF for a predetermined duration.

FAIL-SAFE AND BACKUP FUNCTION



  • The DPF regeneration is prohibited.

PROBABLE CAUSE



  • The exhaust pressure hose or the exhaust pressure pipe is disconnected or damaged.

  • The DPF in the exhaust centre pipe melted down

  • The DPF missing.

DIAGNOSIS PROCEDURE

STEP 1. Check exhaust pressure hose and exhaust pressure pipe.

  • Check the lines between the exhaust differential pressure sensor and the exhaust centre pipe (DPF) (i.e, exhaust pressure hose and exhaust pressure pipe) for disconnection or damage.

Q. Are the check results normal?
Replace the exhaust centre pipe.
Repair or replace the exhaust pressure hose or exhaust pressure pipe.