Code No. P0420: Catalyst Malfunction <Euro5b>


FUNCTION



  • The engine-ECU injects the fuel with the slower timing than usual (post injection), so that the oxygen and HC of exhaust gas burn in the catalyst, and the exhaust gas temperature raises up to the level which enables the DPF regeneration.
  • The engine-ECU monitors the signals from the No. 2 exhaust gas temperature sensor (catalyst temperature) to detect the catalyst inactivation.

TROUBLE JUDGMENT


Check Condition
  • On DPF regeneration
Judgement Criteria
  • The conditions below continues for 30 seconds.
  • The fuel injection amount exceeds the specified value.
  • The engine speed exceeds the specified value.
  • The No. 1 exhaust gas temperature sensor is 350°C or higher.
  • The No. 2 exhaust gas temperature sensor (catalyst temperature) is 450°C or below.

PROBABLE CAUSES



  • Failed No. 1 exhaust gas temperature sensor
  • Failed No. 2 exhaust gas temperature sensor (catalyst temperature)
  • Catalytic converter inactive

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list.

  • Refer to Data List Reference Table .

  1. Item 117: No. 1 exhaust gas temperature sensor
  2. Item 118: No. 2 exhaust gas temperature sensor (catalyst temperature)

Q. Are the check results normal?
Go to Step 2.
Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 2. Forcible DPF regeneration execution

  • Initialise the DPF-related parts, and then delete the diagnosis code (Refer to GROUP 00 - Precautions before Service - Initialisation Procedure for Learning Value in Diesel Particulate Filter (DPF) System ).

  1. Item 42: DPF system malfunction service
  • Carry out the forcible DPF regeneration (Refer to GROUP 17 - Emission Control - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).
    		•

    Q. Is diagnosis code P0420 or P1497 set?
    Replace the catalytic converter. When the catalytic converter is replaced, initialise the learning value. (Refer to GROUP 00 - Precautions before Service - Initialisation Procedure for Learning Value in Diesel Particulate Filter (DPF) System .) On completion, carry out the forcible DPF regeneration (Refer to GROUP 17 - Emission Control - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).
    Replace the engine-ECU. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - Precautions Before Service - 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 ). After registering the injector identification code, carry out the forcible DPF regeneration. (Refer to GROUP 17 - Emission Control - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).