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Service bulletin 09-110-23

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10244906
Published by NHTSA2023-11-06
Manufacturer's number09-110-23
Manufacturer's date2023-10-09
NHTSA componentENGINE AND ENGINE COOLING; EQUIPMENT; ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:CATALYTIC CONVERTOR

NHTSA's summary

This Service Information Bulletin announces diagnostic service procedures to be followed when DTC P0420 (Catalyst System Efficiency Below Threshold Bank 1) is detected by the Engine Control Module (ECM). If DTC P0420 is found to be stored in the ECM, follow the diagnostic procedures outlined below.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Engine, Equipment and accessories, Exhaust and emissions, Catalytic converter

Trouble codes named

P0420

Vehicles listed
SUBARU ASCENT2019, 2020, 2021
SUBARU CROSSTREK2017, 2018, 2019, 2020, 2021, 2022, 2023
SUBARU FORESTER2017, 2018, 2019, 2020, 2021, 2022, 2023
SUBARU IMPREZA2017, 2018, 2019, 2020, 2021, 2022, 2023
SUBARU LEGACY2017, 2018, 2019, 2020, 2021, 2022, 2023
SUBARU OUTBACK2017, 2018, 2019, 2020, 2021, 2022, 2023

Listing a model year does not mean every vehicle of it is concerned: the document says which.