P0300 on the 2020 Mazda CX-9
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.
| 01-001-21-3761a | 2021-08-02. Service bulletin. Some vehicles may exhibit an occasional rough idle accompanied with DTC P0300:00 (Random misfire) due to the following: 1. While closing the EGR valve, carbon deposit etc. pinched at the valve seat prevents the valve from closing completely. 2. The closed position of the EGR valve is learned improperly as it is not equipped with a position sensor. 3. While idling, the EGR gas improperly mixes with fresh air through the EGR valve that is not closed properly. 4. Misfire occurs. To eliminate this concern, the control software of the PCM has been modified (for service) to force the learning of the closed position of the EGR valve when a misfire is detected at idle. |
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1 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.