This bulletin applies to 2016-2021 CX-9 and 2018-2019 Mazda6 vehicles, equipped with SKYACTIV-G 2.5L engines. Some vehicles may exhibit an occasional rough idle accompanied by DTC P0300:00 (random misfire) due to the following:
1. While closing the EGR valve, carbon deposits may be pinched at the valve seat, preventing 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 the concern, reprogram the PCM. The control software of the PCM has been modified to force the learning of the closed position of the EGR valve when a misfire is detected at idle.
If the EGR valve is to be cleaned, replace the gasket P/N PY8V-20-305. If the EGR is to be replaced, use P/N PY8V-20-300.
