Subaru bulletin 09-110-23R
What it saysThis 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). NHTSA’s full summary ↓
Subaru filed this with NHTSA as a service bulletin dated Nov 7, 2023, received Dec 5, 2023, about the engine. It names 43 model years (2017–2023). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis 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).
Trouble codes it names: P0420 P0037 P0038 P0131 P0132 P0134 P0137 P0138 P0140 P0171 P0172 10 of 11 read from the document itself
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 09-110-23R | Service bulletin | Nov 7, 2023 | 10246083 | PDF, 2,023 KB |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themand 3 more on this site: 2020 Subaru WRX, 2019 Subaru WRX, 2018 Subaru WRX.
A vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
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What owners reported
Source: NHTSA complaint databaseOwners of the 43 model years this bulletin names have filed 10,373 complaints with NHTSA since 2015. 840 of them name Engine — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
On the 2017 Subaru Forester, the 27 owners who gave an odometer reading for Engine reported it at a median of 20,000 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.
At around the 2000 mile mark I noticed a drastic reduction in fuel econemy. I also started noticing metal particles in the engine oil. I also noticed a significant drop in engine power as well. This is a sign of debris getting in the engine and causing metal particles to become broken off. My mileage went from 460-480 mpt to 360-380 mpt.
2019 Subaru Crosstrek · Engine · filed with NHTSA Oct 27, 2019
I would just like to complain about the excess Rtv on the engine oil pan that has been demonstrated on numerous videos of people opening up the oil drain pan and finding chunks of Rtv blocking some of the engine oil pickup tube. I have not opened up my oil drain pan due to cost. This has not lead to failure as of yet but it is worrisome.
2023 Subaru WRX · Engine · filed with NHTSA Jul 18, 2024
To Whom It May Concern, I am filing a formal dispute and safety complaint regarding my 2022 Subaru Crosstrek Limited. On November 12, 2025, while driving at approximately 70 mph on the highway, the vehicle suddenly stopped operating automatically without warning. This was a terrifying and dangerous event for me and my family.
2022 Subaru Crosstrek · Engine · filed with NHTSA Nov 12, 2025
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the engine
Source: same model, same component group54 other manufacturer communications filed against these Subaru models under the same component group (engine), newest first. The eight newest are listed; the rest are on the Subaru list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| 09-98-22R | Service bulletin | Aug 31, 2026 | This bulletin announces the availability of new reprograming files for the Engine Control Module (ECM) developed to remedy the following DTC… |
| 02-196-26R | Service bulletin | Aug 20, 2026 | This service bulletin outlines the diagnostic and repair procedure for white smoke emitted from the exhaust after startup. This is an revise… |
| 07-231-26 | Service bulletin | Aug 5, 2026 | This bulletin announces the service procedure for battery replacement on 2025-2026MY Impreza and Crosstrek. |
| 02-193-24R | Service bulletin | Jun 30, 2026 | This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel inject… |
| 09-74-21R | Service bulletin | Jun 26, 2026 | This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel inject… |
| 02-196-26 | Service bulletin | Jun 23, 2026 | This bulletin outlines the diagnostic and repair procedure for white smoke emitted from the exhaust after startup. |
| 18-243-26 | Service bulletin | Jun 11, 2026 | This bulletin announces the elimination of oil spacers from both left- and right side camshaft carriers on FB2.5 engines. |
| 09-130-25R | Service bulletin | Jun 3, 2026 | This bulletin announces the design change made to the exhaust manifold flange nut material that has been changed from stainless steel to med… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Subaru, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Subaru 09-110-23R a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the 09-110-23R repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way.
Which vehicles does 09-110-23R cover?
The manufacturer filed it against 43 model years: 2021 Subaru Ascent, 2020 Subaru Ascent, 2019 Subaru Ascent, 2023 Subaru Crosstrek, 2022 Subaru Crosstrek, 2021 Subaru Crosstrek and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.