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P0420 on the 2018 Honda Fit

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

Nobody has written a description of this code yet.

Bulletins for this model year that name P0420
ATI&050320249052024-05-15. Other. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 [Catalyst System Efficiency Below Threshold] stored. To better understand the cause of this condition, AHM would like to inspect the vehicle prior to your attempting a repair of any kind.
ATI&041520249022024-04-17. Service bulletin. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 [Catalyst System Efficiency Below Threshold] stored. To better understand the cause of this condition, AHM would like to inspect the vehicle prior to your attempting a repair of any kind.
ATI&032820249022024-04-02. Service bulletin. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 [Catalyst System Efficiency Below Threshold] stored. To better understand the cause of this condition, AHM would like to inspect the vehicle prior to your attempting a repair of any kind.
ATI&021520249052024-02-27. Service bulletin. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2017-2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 (Catalyst System Efficiency Below Threshold) stored. To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.
ATI&020120249042024-02-15. Service bulletin. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2017-2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 (Catalyst System Efficiency Below Threshold) stored. To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.
ATI&011720249052024-01-26. Service bulletin. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2017-2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 (Catalyst System Efficiency Below Threshold) stored. To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.
ATI&010220249092024-01-09. Service bulletin. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2017-2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 (Catalyst System Efficiency Below Threshold) stored. To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.
ATI&112820239102023-12-08. Service bulletin. Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2017-2018 Fits with customer complaint of Check Engine Light (CEL) on with DTC P0420 (Catalyst System Efficiency Below Threshold) stored. To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.

8 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.