DTC P0420

DTC P0420  : Catalyst System Efficiency Below Threshold

NOTE: 

• Before you troubleshoot, review the general troubleshooting information .
• If some of the DTCs listed below are stored at the same time as DTC P0420, troubleshoot them first, then recheck for DTC P0420.
• • -

    P0137, P0138, P0139, P2270, P2A01: Secondary HO2S (Sensor 2)

  • -

    P0141: Secondary HO2S (Sensor 2) heater

  • -

    P0300: Random misfire

  • -

    P0301, P0302, P0303, P0304: No. 1, No. 2, No. 3, No. 4 cylinder misfire detected

• Poor quality fuel may cause this DTC.

DTC (PGM-FI)

1. DTC check

   -1. Turn the vehicle to the ON mode.

   -2. Check for Pending or Confirmed DTCs with the HDS.

   DTC Description	Confirmed DTC	Pending DTC
   P0420 Catalyst System Efficiency Below Threshold

   Is Confirmed DTC P0420 indicated?

   YES (Confirmed DTC is indicated)

   Replace the catalytic converter .

   NO (Pending DTC is indicated)

   Check the installation of the catalytic converter, then recheck.