Code No. P0420: Catalyst Malfunction

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

• On DPF regeneration
  

• 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.
  

FAIL-SAFE AND BACKUP FUNCTION

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

PROBABLE CAUSES

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

	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 ).

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 Common Rail Engine <4N1> ). On completion, carry out the forcible DPF regeneration (Refer to GROUP 17 - Emission Control <DIESEL> - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).

	Replace the engine-ECU.