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Service bulletin 09-131-25

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 id11017434
Published by NHTSA2025-05-01
Manufacturer's number09-131-25
Manufacturer's date2025-04-08
NHTSA componentENGINE; ELECTRICAL SYSTEM

NHTSA's summary

This bulletin announces the diagnostic procedures and availability of reprograming files to rectify the following Diagnostic Trouble Codes (DTCs). The ELCM may accumulate condensation causing the inaccurate detection of P2404. P0420 may become falsely detected due to unstable combustion caused by a downshift. The new reprogramming files contains enhanced software allowing for condensation conditions and downshift rotational speeds be more accurately 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

Electrical system, Engine

Trouble codes named

P0420, P2404

Vehicles listed
SUBARU WRX STI2015, 2016, 2017, 2018, 2019, 2020, 2021 (the catalog's model; the bulletin names a series or trim of it)

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

Recalls for the same vehicles and component
17V6250002017-10-06. ELECTRICAL SYSTEM:WIRING
16V1620002016-03-21. ENGINE AND ENGINE COOLING:ENGINE:GASOLINE:TURBO/SUPERCHARGER

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
SubaruNet Announcement (M2026-10-05. Other. This announcement provides information on a new software update for the Midtronics Dss and DCA machines.
18-244-262026-10-05. Service bulletin. "This Bulletin announces additional troubleshooting steps for the following DTCs: DTC C1956: RH Actuator Circuit DTC C1957: LH Actuator Circuit"
15-333-25R2026-10-05. Service bulletin. This bulletin contains illustrations of exchange components and their manufacturer as well as a description of the proper exchange procedure. This is an revised version of the original bulletin.
15-322-25R2026-10-05. Service bulletin. In the interest of customer satisfaction, Subaru of America, Inc. (SOA) is extending the New Car Limited Warranty coverage for the CP1 & Gen 3.1 Head Unit used in the listed models and model years to (8) eight years / 150,000 miles to cover certain qualifying repairs to the infotainment audio system. This is an revised version of the original bulletin.
15-304-22R2026-10-05. Service bulletin. This bulletin has been developed to outline the steps for gathering basic but essential information during diagnosis of Infotainment concerns. This is an revised version of the original bulletin.
15-308-23R2026-09-03. Service bulletin. This Service Information Bulletin outlines a systematic procedure for diagnosing parasitic draw (dark/standby current) in vehicles experiencing battery drain when the ignition is off, leading to no-start conditions or frequent jump-starts.This is an revised version of the original bulletin.
15-304-22R2026-09-03. Service bulletin. This Bulletin has been developed to outline the steps for gathering basic but essential information during diagnosis of Infotainment concerns. (This is an revised version of the original bulletin.)
Article Locator2026-09-03. Other. Techtips newsletter locator index.
15-333-25R2026-09-03. Service bulletin. This bulletin contains illustrations of exchange components and their manufacturer as well as a description of the proper exchange procedure. 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.)