Posted in MMC L200

P0420 – Catalyst Malfunction MMC L200 IV

 Posted by  Posted on September 28, 2020

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.

    • 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.

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

    • Q. Are the check results normal?

    STEP 2. Forcible DPF regeneration execution

  • Item 42: DPF system malfunction service

    • Q. Is diagnosis code P0420 or P1497 set?

    Author: admin