MAZDA

01-001-26b

2026-03-04 · NHTSA 11030598

A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.

Manufacturer summary

Original wording in English

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. Vehicles with SKYACTIV-G 2.5T are not applicable to this service information. DTC P0126:00 is not required to be present to perform this repair. If the vehicle has not previously had the repair specified in this TSB and is exhibiting any of the listed symptoms, proceed with the repair procedure outlined in this bulletin. If DTC P2B61:00 (Coolant Control Valve Circuit Range/Performance) is present along with DTC P0126:00, this TSB does not apply. Diagnose the symptom and/or stored DTCs according to the procedures in MGSS. If only DTC P0126:00 is present and this TSB has already been completed previously, this bulletin does not apply, diagnose the symptom and/or stored DTCs according to the procedures in MGSS. This concern may be caused if the coolant control valve fail-safe thermostat opens at a temperature lower than the normal temperature due to a deformation of the thermostat diaphragm. To eliminate the concern, the water flow control valve specification has been modified. Affected vehicles will require PCM reprogramming with the Mazda Modular Diagnostic System (M-MDS), using either a) Mazda Diagnostic and Repair Software (MDARS) or b) Mazda Integrated Diagnostic System (IDS) 140.04 or later software.

Repeated filings are grouped only when make, bulletin number, publication date and complete summary agree. Original record numbers are retained. Older publications remain available, and an explicit later version is shown when established. Pre-1994 vehicle associations are separated from default results; an unspecified year does not mean all model years apply.