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Service bulletins for the 2018 Mazda Mazda3

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.

462 on file from NHTSA, as of 2026-10-19.

About P0126 on the 2018 Mazda Mazda3: what the code means, and the bulletins and recalls about the same components.

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Only bulletins with trouble code: P0126 are shown. Show all

Bulletins, newest first
01-005-24 Dlr Ltr2024-07-05. Other. 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. NOTE: Vehicles with SKYACTIV-G 2.5T are not applicable to this service information. If DTC P2B61:00 (Coolant control valve circuit range/performance) accompanies DTC P0126:00, this TSB is not applicable. Diagnose DTCs according to the instructions on MGSS online.
SA-017-21a2021-04-06. Service bulletin. ENGINE AND ENGINE COOLING; EQUIPMENT. CHECK ENGINE LIGHT ON WITH DTC P0126:00 AND ENGINE RUNNING COOLER THAN NORMAL / POOR HEATER PERFORMANCE / LOW ENGINE COOLANT TEMPERATURE (BLUE) LIGHT ON: Some customers may experience the CHECK ENGINE LIGHT ON with DTC P0126:00 (Thermostat stuck open) and one or more of the following symptoms: The engine takes longer to warm up. The engine temperature gauge fluctuates. The low coolant temperature indicator (blue) light stays on longer or comes on while driving. Poor heater performance, especially at idle.
SA-017-212021-03-03. Service bulletin. ENGINE AND ENGINE COOLING. Some customers may experience the CHECK ENGINE LIGHT ON with DTC P0126:00 (Thermostat stuck open) and one or more of the following symptoms: The engine takes longer to warm up. The engine temperature gauge fluctuates. The low coolant temperature indicator (blue) light stays on longer or comes on while driving. Poor heater performance, especially at idle.
SA-035-20b2021-01-06. Service bulletin. EQUIPMENT; ENGINE AND ENGINE COOLING. Some customers may experience the CHECK ENGINE LIGHT ON with DTC P0126:00 (Thermostat stuck open) and one or more of the following symptoms: The engine takes longer to warm up. The engine temperature gauge fluctuates. The low coolant temperature indicator (blue) light stays on longer or comes on while driving. Poor heater performance, especially at idle.

The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.