P0128 on Subaru vehicles The engine is not reaching its normal operating temperature in the expected time — usually the thermostat
P0128 is named on 7 Subaru model years (2019–2022): 7 manufacturer filings and 1 owner report in NHTSA’s files, across Forester, Ascent.
Which Subaru model years name P0128
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports |
|---|---|---|---|
| 2020 Subaru Forester | Electrical System | 1 | 1 |
| 2022 Subaru Ascent | Electrical System | 1 | — |
| 2021 Subaru Ascent | Electrical System | 1 | — |
| 2021 Subaru Forester | Engine | 1 | — |
| 2020 Subaru Ascent | Engine | 1 | — |
| 2019 Subaru Ascent | Engine | 1 | — |
| 2019 Subaru Forester | Electrical System | 1 | — |
A model year is listed because the code is named in its own record — a bulletin filed against it, or an owner’s complaint about it — not because every one of these vehicles sets it. Counts are documents in NHTSA’s files, not failure rates.
Subaru filings that name P0128
Source: NHTSA manufacturer communicationsBulletins and campaigns Subaru filed with NHTSA whose summary names P0128. Quote the document number at the service desk — it is a diagnosis the maker has already written down.
- 09-75-21 Service bulletin2021-07-28 · Electrical System
- This bulletin announces the availability of NEW reprogramming files to correct DTC P0128.
- 09-98-22R Service bulletin2026-08-31 · Electrical System
- 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.
What P0128 means
Source: SAE J2012 / OBD-IIThe engine is not reaching its normal operating temperature in the expected time — usually the thermostat.
A stored code names the test that failed, never the part that caused it. The record above is what Subaru and its owners have filed about it; the code’s page across every make has the whole file.
Common questions
Source: NHTSA files and the OBD-II standardIs P0128 a known problem on Subaru vehicles?
It is a documented one: NHTSA's files hold 7 manufacturer filings and 1 owner report naming P0128 on 7 Subaru model years (2019–2022). Whether it is a problem on one particular car is a diagnosis, not a count — but a bulletin that names the code on your model year is the place to start.
Which Subaru models does P0128 appear on most?
2020 Forester (2 documents), 2022 Ascent (1 document), 2021 Ascent (1 document).
Does P0128 on a Subaru mean it is recalled?
No. Recalls are filed by campaign and matched by VIN; no recall is triggered by a scan tool. Check the VIN at nhtsa.gov/recalls, or open the model year's page here for the campaigns filed against it.