Closing Mazda EGR

Some 2016-2021 Mazda CX-9 vehicles with Skyactive-G 2.5T produced before Jan. 26, 2021 may exhibit an occasional rough idle along with DTC P0300:00 (random misfire). This could be due to carbon deposits pinched at the EGR valve seat, preventing the EGR from closing.

Information courtesy of Mitchell 1

Mike Mavrigian

Oct. 24, 2022

The closed position of the EGR valve is learned improperly as it is not equipped with a position sensor; when idling, the EGR gas improperly mixes with fresh air through the EGR valve that is not closed properly.

To eliminate this concern, the PCM control software has been modified to force the learning of the closed position of the EGR valve when a misfire is detected at idle. Reprogram the PCM with Mazda Modular Diagnostic System (M-MDS) using IDS 122.05 or later software.

About the Author

Information courtesy of Mitchell 1

Information for Technical Service Bulletins comes from ProDemand, Mitchell 1's auto repair information software for domestic and import vehicles. Headquartered in San Diego, Mitchell 1 has provided quality repair information solutions to the automotive industry since 1918.

Mike Mavrigian

Motor Age Editor

Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety of specialties, 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.