Subaru Ascent 2017–2023 — technical service bulletin
Bulletin 09-110-23 · NHTSA communication 10244906 · issued Oct 9, 2023
Technical service bulletin
communication type
Engine and Engine Cooling
component
2017–2023
model years
38
vehicle entries
Official 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.
Vehicles covered
- 2019 Subaru Ascent
- 2020 Subaru Ascent
- 2021 Subaru Ascent
- 2017 Subaru Crosstrek
- 2018 Subaru Crosstrek
- 2019 Subaru Crosstrek
- 2020 Subaru Crosstrek
- 2021 Subaru Crosstrek
- 2022 Subaru Crosstrek
- 2023 Subaru Crosstrek
- 2017 Subaru Forester
- 2018 Subaru Forester
- 2019 Subaru Forester
- 2020 Subaru Forester
- 2021 Subaru Forester
- 2022 Subaru Forester
- 2023 Subaru Forester
- 2017 Subaru Impreza
- 2018 Subaru Impreza
- 2019 Subaru Impreza
- 2020 Subaru Impreza
- 2021 Subaru Impreza
- 2022 Subaru Impreza
- 2023 Subaru Impreza
- 2017 Subaru Legacy
- 2018 Subaru Legacy
- 2019 Subaru Legacy
- 2020 Subaru Legacy
- 2021 Subaru Legacy
- 2022 Subaru Legacy
- 2023 Subaru Legacy
- 2017 Subaru Outback
- 2018 Subaru Outback
- 2019 Subaru Outback
- 2020 Subaru Outback
- 2021 Subaru Outback
- 2022 Subaru Outback
- 2023 Subaru Outback
What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.