Service bulletins for the 2020 Mazda CX-9
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.
327 on file from NHTSA, as of 2026-10-19.
About P0300 on the 2020 Mazda CX-9: what the code means, and the bulletins and recalls about the same components.
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Only bulletins with trouble code: P0300 are shown. Show all
| 01-001-21-3761a | 2021-08-02. Service bulletin. ENGINE AND ENGINE COOLING. 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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The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.