There are 3 owner-reported engine complaints for the 2020 Mazda CX-9in NHTSA's database. These are unverified consumer reports and may not reflect confirmed defects.
Excessive oil consumption. In less than 3000 miles, I have to add a quart of oil
Some vehicles may have coolant leaks at the cylinder head around the exhaust manifold. There may be cracks at the stud bolt hole or at the outside of the exhaust manifold - from Mazda's TSB. Excessive coolant leak leading to engine-overheating and going into 'limp mode' couldn't drive faster than around 30 mph. Mazda has repeatedly declined help with goodwill requests and any further assistance. ref. https: [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
THE MAZDA CX-9 UNCOMMANDED ENGINE ACCELERATION REPORTED HEREIN DID NOT RESULT IN ANY DAMAGE PRIMARILY BECAUSE IT COMMENCED SEVERAL SECONDS AFTER I BEGAN LIGHT BRAKING WHILE APPROACHING A RED TRAFFIC LIGHT. MY IMMEDIATE RESPONSE WAS TO INCREASE BRAKE PRESSURE; THERE WAS NO NEED FOR ME TO MOVE MY LEG OTHER THAN PRESSING HARDER WITH MY FOOT. MY FOOT HAD BEEN OFF THE ACCELERATOR FOR MANY SECONDS WHILE ALLOWING THE CAR TO SLOWLY DECELERATE WHILE COASTING TOWARD TRAFFIC STOPPED AT A RED LIGHT. WITHIN TWO SECONDS OF COMMENCEMENT OF UNCOMMANDED ENGINE ACCELERATION AND WITH THE CAR FULLY STOPPED, I SHIFTED THE TRANSMISSION INTO NEUTRAL. THE ENGINE IMMEDIATELY GENERATED THE NOISE OF VERY HIGH RPM. ALTHOUGH THE DASHBOARD INCLUDES A TACHOMETER, I DID NOT IMMEDIATELY THINK TO LOOK AT IT; INSTEAD, I TURNED THE IGNITION OFF. A FEW SECONDS LATER, I SHIFTED THE TRANSMISSION INTO PARK AND RESTARTED THE CAR WHICH OPERATED NORMALLY THEREAFTER. MY FOOT DID NOT MOVE OFF THE BRAKE PEDAL DURING ANY OF THE PRECEDING SEQUENCE. ONLY THE NHTSA AND POSSIBLY THE MANUFACTURER WOULD KNOW IF THIS IS A ONE IN A BILLION-HOURS OR A MORE COMMON OCCURRENCE. I AM WILLING TO ANSWER ANY QUESTIONS THE NHTSA OR THE MANUFACTURER MIGHT HAVE. I GRADUATED FROM MIT, WORKED OVER 29 YEARS FOR THE LEADING USA COMMERCIAL AIRCRAFT MANUFACTURER AND AM CURRENTLY RETIRED.
Complaints are unverified consumer reports submitted to NHTSA. A high complaint count may reflect vehicle popularity, not defect severity. Data sourced from NHTSA public records.
Data synced from NHTSA on Apr 26, 2026