P0126
7 owner reports and 798 manufacturer filings across 32 model years from Mazda.
Where P0126 shows up
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports | Parts |
|---|---|---|---|---|
| 2019 Mazda CX-5 | Engine | 36 | 2 | |
| 2020 Mazda CX-5 | Engine | 36 | 1 | |
| 2020 Mazda Mazda6 | Engine | 37 | — | |
| 2019 Mazda Mazda6 | Engine | 37 | — | |
| 2018 Mazda CX-5 | Engine | 36 | — | |
| 2019 Mazda Mazda3 | Engine | 35 | 1 | |
| 2020 Mazda CX-3 | Engine | 35 | — | |
| 2019 Mazda CX-3 | Engine | 35 | — | |
| 2020 Mazda CX-30 | Engine | 35 | — | |
| 2020 Mazda Mazda3 | Engine | 35 | — | |
| 2018 Mazda Mazda6 | Engine | 35 | — | |
| 2021 Mazda CX-5 | Engine | 31 | 2 | |
| 2021 Mazda CX-3 | Engine | 32 | — | |
| 2021 Mazda CX-30 | Engine | 32 | — | |
| 2021 Mazda Mazda6 | Engine | 32 | — | |
| 2021 Mazda Mazda3 | Engine | 31 | — | |
| 2022 Mazda CX-30 | Engine | 29 | — | |
| 2022 Mazda Mazda3 | Engine | 29 | — | |
| 2023 Mazda CX-30 | Engine | 28 | — | |
| 2023 Mazda CX-5 | Engine | 27 | 1 | |
| 2022 Mazda CX-5 | Engine | 28 | — | |
| 2023 Mazda Mazda3 | Engine | 28 | — | |
| 2024 Mazda CX-5 | Engine | 27 | — | |
| 2025 Mazda CX-5 | Engine | 21 | — | |
| 2026 Mazda CX-30 | Engine | 6 | — |
Showing the 25 model years where P0126 appears most; it is on file for 32 in total.
A model year appears here because the code is named in its record, not because every one of these vehicles sets it. Counts are mentions in the federal files, not failure rates — nobody publishes the denominator.
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P0126 by make
The same record, one make at a time: the model years, bulletins and owner reports that name P0126 on that maker’s vehicles.
What it gets filed under
What owners said
Source: NHTSA complaint databaseOwners’ own words, one per nameplate, scrubbed of anything identifying. These are unverified reports filed with NHTSA — they are what was said, not a finding that it was true.
Summary of Events: Purchase Date: 05/27/2023 Coolant Warning: In January 2025, I received a coolant temperature warning (code P0126) indicating insufficient coolant temperature
When I took it to a dealer, they stated that the check engine light must come on from DTC P0126:00 before they can address the problem under warranty
798 manufacturer filings name P0126. Start with what the maker wrote down.
A code names the test that failed, not the part. A bulletin that names it is often a diagnosis someone has already written down — quote its number at the service desk.
Manufacturer filings that name it
Source: NHTSA manufacturer communicationsService bulletins and campaigns whose filed summary names P0126.
- DRW59 Dlr Ltr Service campaign2026-03-25 · Engine
- Subject: Notification of Dealer Re-Work (DRW59) – 2026MY CX-30 and 2026MY Mazda3 - Check Engine Light On With DTC P0126:00 Dear Mazda Dealer Colleagues, Mazda Motor Corporation has decided to conduct a Dealer Re-Work on certain 2026MY CX-30 and Mazda3 vehicles. Concern Outline: On certain subject vehicles, the check engine light may illuminate with DTC P0126:00 (Thermostat stuck open) stored du
- 01-006-26 Service bulletin2026-03-11 · Unknown Or Other
- Some customers may experience the check engine light on with DTC P0126:00 (Thermostat stuck open) stored. This is due to improper PCM logic control. To eliminate the concern, the PCM control software has been modified. REPAIR PROCEDURE 1. Verify the customer concern. 2. Reprogram the ECU with the Mazda Modular Diagnostic System (M-MDS), using Mazda Diagnostic and Repair Software (MDARS). Refer to
- SSPD8 Parts and Warr a Warranty extension2026-01-30 · Engine
- SSPD8 - Check Engine Light ON with DTC P0126:00 - WARRANTY EXTENSION For certain 2018-2025MY CX-5, 2019-2023MY Mazda3, 2019-2022MY CX-3, 2018-2021MY Mazda6, 2020-2023MY CX-30 that are equipped with the suspected coolant control valve, the warranty coverage for specific repair of the fail-safe thermostat is extended to: 15 years (180 months) or 150,000 miles (240,000 km) whichever comes first, from
- SA-062-25 Service bulletin2025-12-20 · Engine
- Some vehicles equipped with a countermeasure Coolant Control Valve (plug in place of the thermostat inside the CCV) may experience a DTC P0126:00.
- 01-005-24c Service bulletin2024-11-05 · Engine
- Some customers may experience a check engine light ON with DTC P0126:00 (Thermostat stuck open) and one or more of the following symptoms: Engine takes longer to warm up. Engine temperature gauge fluctuates. Low coolant temperature indicator (blue) light stays on longer or turns on while driving. Poor heater performance, especially at idle.
- SSPD8 Repair Warranty extension2024-10-31 · Engine
- Mazda Motor Corporation has decided to conduct a Special Service Program (SSP) to extend the warranty coverage for a specific repair of the fail-safe thermostat in the coolant control valve on certain CX-5, Mazda3, CX-3, Mazda6 and CX-30 vehicles that are equipped with the suspected coolant control valve. The warranty coverage for a specific repair of fail-safe thermostat has been extended to 15 y
What P0126 means
Source: SAE J2012 / OBD-IIP0126 sits in the generic range of the OBD-II standard, so it means the same thing on every vehicle sold in the United States — but WhichTrim does not carry a definition for it and will not invent one. What is on this page is the record: who named it and on what.
A stored code names the test that failed, never the part that caused it. It is the starting point of a diagnosis, not its conclusion — the same code has several possible causes and the cheap one is not always right.
Common questions about P0126
Source: NHTSA files and the OBD-II standardCan I keep driving with P0126 stored?
Nobody can answer that from the code alone, and a site that does is guessing. A steady light means a fault was logged and the car should be checked soon; a flashing light means a severe misfire — slow down and get it seen as soon as possible, because severe misfire can quickly damage the catalytic converter. The safe read of this page is the mileage and the components, not permission.
Does a code mean the car is recalled?
No. Recalls are filed by campaign and matched by VIN, and none of them are triggered by a scan tool. If you want to know whether an open recall applies to one specific vehicle, check the VIN at nhtsa.gov/recalls — that is the only source that settles it.
Why do the counts here differ from other sites?
Because these are not estimates. Every number on this page is a count of documents in NHTSA's own files: manufacturer communications that name the code in their filed summary, and owner complaints that name it in the narrative. We do not model, weight or extrapolate them.
Will clearing the code fix it?
Clearing turns the light off and erases the freeze-frame data a technician would have used to work out what happened. If the condition is still there the code returns, usually within a few drive cycles, and the diagnosis now starts from less information than before.