Service bulletins for the 2021 Mazda CX-3
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.
278 on file from NHTSA, as of 2026-10-19.
About P0126 on the 2021 Mazda CX-3: 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
| 01-005-24a | 2024-07-05. Service bulletin. 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. |
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| 01-005-24 | 2024-07-05. Service bulletin. 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. |
| 01-005-23a | 2024-01-06. 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 |
| 01-005-23 | 2023-03-03. 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. NOTE: Vehicles with SKYACTIV-G 2.5T are not applicable. If DTC P2B61:00 (Coolant control valve circuit range/performance) accompanies DTC P0126:00, this TSB is not applicable. Diagnose according to the instructions on MGSS online. Due to production variety of the failsafe thermostat integrated in the coolant control valve, engine coolant may enter into a dry hollow in the failsafe thermostat, resulting in unintended opening of the failsafe thermostat at lower temperatures (104-176 °F (40-80 °C)). To eliminate this concern, the production process of the coolant control valve has been modified. |
| 01-013-22 | 2022-11-04. 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 NOTE: * Vehicles with SKYACTIV-G 2.5T are not applicable. * If DTC P2B61:00 (Coolant control valve circuit range/performance) accompanies, this information is not applicable. Diagnose according to the instructions in MGSS. Due to production variety of the failsafe thermostat integrated in the coolant control valve, engine coolant may enter into a dry hollow in the failsafe thermostat, resulting in unintended opening of the failsafe thermostat at lower temperatures (104-176 °F (40-80 °C)). To eliminate this concern, the production process of the coolant control valve has been modified. |
| 01-011-21-3800a | 2021-10-02. Service bulletin. EQUIPMENT ADAPTIVE/MOBILITY; 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. NOTE: Vehicles with SKYACTIV-G 2.5T are not applicable. Due to production variety of the failsafe thermostat integrated in the coolant control valve, engine coolant may enter into a dry hollow in the failsafe thermostat, resulting in unintended opening of the failsafe thermostat at lower temperatures (104-176 °F (40-80 °C)). To eliminate this concern, the production process of the coolant control valve has been modified. |
| 01-011-21-3800 | 2021-04-26. 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. NOTE: Vehicles with SKYACTIV-G 2.5T are not applicable. Due to production variety of the failsafe thermostat integrated in the coolant control valve, engine coolant may enter into a dry hollow in the failsafe thermostat, resulting in unintended opening of the failsafe thermostat at lower temperatures (104-176 °F (40-80 °C)). To eliminate this concern, the production process of the coolant control valve has been modified. |
The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.