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Service bulletin 09-110-23R

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 id10246083
Published by NHTSA2023-12-05
Manufacturer's number09-110-23R
Manufacturer's date2023-11-07
NHTSA componentEQUIPMENT; ENGINE AND ENGINE COOLING

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).

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

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
SUBARU WRX2018, 2019, 2020, 2021, 2022, 2023

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

Recalls for the same vehicles and component
26V4360002026-07-07. EQUIPMENT:OTHER:LABELS
23V0160002023-01-23. EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL
22V4730002022-07-01. ENGINE AND ENGINE COOLING:ENGINE:ENGINE CONTROL MODULE (ECU/ECM); ELECTRICAL SYSTEM:WIRING
21V2640002021-04-15. ELECTRICAL SYSTEM:SOFTWARE; ENGINE AND ENGINE COOLING:ENGINE:ENGINE CONTROL MODULE (ECU/ECM):SOFTWARE; ELECTRICAL SYSTEM:IGNITION; ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:MANIFOLD/HEADER/MUFFLER/TAIL PIPE
20196042019-12-02. Engine
19V8560002019-12-02. ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:CRANKCASE (PCV)
20195362019-10-25. Accessories
20195272019-10-17. Engine
20195262019-10-17. Engine
20195252019-10-17. Engine

A recall listed here may apply to some of the same vehicles. Only the manufacturer can say whether it applies to one vehicle.

Other bulletins for the same vehicles and component
09-141-262026-10-05. Service bulletin. This Bulletin provides a diagnostic procedure for customer concerns about hesitation, reduced acceleration, or lack of power when driving uphill or under heavy engine load.
09-84-22R2026-10-05. Service bulletin. This bulletin announces Warranty Extension and design changes made to the front exhaust pipe and covers to address the concerns of some customers regarding an odor or a rattle-type noise/fluttering sound coming from the undercarriage, during acceleration. This is an revised version of the original bulletin.
09-98-22R2026-09-03. Service bulletin. This bulletin announces the availability of new reprograming files for the Engine Control Module (ECM) developed to remedy the following DTCs: P0016, P0017, P0018, P0019, P0014, P0024, P0128, P2109. If any of the DTCs listed above are found to be stored in the ECM, follow the procedures outlined in the bulletin. This is an revised version of the original bulletin.
02-196-26R2026-09-03. Service bulletin. This service bulletin outlines the diagnostic and repair procedure for white smoke emitted from the exhaust after startup. This is an revised version of the original bulletin.
02-193-24R2026-07-02. Service bulletin. This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers). (This is an revised version of the original bulletin.)
09-74-21R2026-07-02. Service bulletin. This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers). (This is an revised version of the original bulletin.)
02-196-262026-07-02. Service bulletin. This bulletin outlines the diagnostic and repair procedure for white smoke emitted from the exhaust after startup.
09-130-25R2026-07-02. Service bulletin. This bulletin announces the design change made to the exhaust manifold flange nut material that has been changed from stainless steel to medium carbon steel. This change also necessitates a revised tightening torque specification. (This is an revised version of the original bulletin.)
02-195-262026-07-01. Service bulletin. This bulletin announces the availability of reprogramming files for the Engine Control Module (ECM) for certain vehicles equipped with 3.6L engines.
18-240-262026-07-01. Service bulletin. "This bulletin provides a new diagnostic procedure for vehicles equipped with a Denso CP 1, 1.5 and 2.5 head units to provide an enhanced version of the troubleshooting steps for Sound does not come out from the speaker."