To eliminate this concern, the control software of the PCM has been modified to force the learning of the closed position of the EGR valve when a misfire at idle is detected.
This bulletin applies to 2018 Mazda6, 2019 Mazda6, and 2016-2021 CX-9 vehicles. Some vehicles may exhibit an occasional rough idle accompanied by DTC P0300:00 (random misfire). This may be due to carbon deposits in the EGR valve while closing, pinching the valve seat and preventing the valve from closing completely; the closed position of the EGR valve is learned improperly, as it is not equipped with a position sensor; or while idling, the EGR gas improperly mixes with fresh air through the valve that is not closed properly.
To eliminate this concern, the control software of the PCM has been modified to force the learning of the closed position of the EGR valve when a misfire at idle is detected.
If the concern continues even after cycling the engine on and off, check the EGR valve and clean the carbon deposit if it prevents the valve from closing. Reprogram the PCM with Mazda Modular Diagnostic System (M-MDS) using IDS 122.05 or later software.
Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety ofspecialties, from engine building to wheel alignment, and has authored more than a dozen books that crisscross the automotive spectrum. Mike operates Birchwood Automotive, an Ohio shop that builds custom engines and performs vintage vehicle restorations. The shop also features a professional photo studio to document projects and to create images for articles and books.
