# P0126 on the 2018 Mazda Mazda3

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

Nobody has written a description of this code yet.

## Bulletins for this model year that name P0126

- [11003351](https://open.wenmarpro.com/bulletins/11003351), 2024-07-05: 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.
- [10189949](https://open.wenmarpro.com/bulletins/10189949), 2021-04-06: 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.
- [10188024](https://open.wenmarpro.com/bulletins/10188024), 2021-03-03: 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.
- [10185185](https://open.wenmarpro.com/bulletins/10185185), 2021-01-06: 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.