2021 Mazda CX-9 Engine Problems

Mileage when the problem started

Owner reports

Selected complaints filed with NHTSA by 2021 Mazda CX-9 owners, lightly cleaned up (personal details are redacted by NHTSA).

The contact owns a 2021 Mazda CX-9. The contact stated that while accelerating quickly and entering the highway, there was no motive power to the vehicle. While crossing the highway in the right lane, driving at 65 MPH, the vehicle in front moved over; there was a parked vehicle. The contact was able to stop the vehicle before causing a crash. The driver was starting to accelerate, but there was no motive power when the accelerator pedal was depressed. The smart brake system malfunction message was displayed. There were no warning lights illuminated. The contact called the local dealer, who scheduled an appointment. The vehicle was not diagnosed or repaired. The manufacturer was contacted and informed the contact to have the vehicle diagnosed. The failure mileage was approximately 53,186.

The contact owns a 2021 Mazda CX-9. The contact stated that while driving at 60 MPH or exceeding 60 MPH, the vehicle would lose motive power and stall without warning. The contact stated that he would coast to the side of the road and the vehicle would restart after 2-3 attempts and regain normal functionality. The vehicle had not been diagnosed or repaired. The manufacturer was not made aware of the failure. The approximate failure mileage was 49,000.

The vehicle was parked stationary in the driveway with the engine running for 3-5 minutes with the A/C on. The vehicle then accelerated forward into my garage causing damage. Once I entered the vehicle, both the dash and shifter displayed park. Current TCU system internal failures have been reported from the pulling of data from Mazda.

1000 miles before first ever oil change was needed (according to window sticker provided by Mazda) the low engine oil light came on. The oil was low and needed to be toped off and brought directly to dealer for oil change. The same thing happened again 1300 miles before second oil change was required. It became obvious that the brand new vehicle was burning oil for some reason. The dealership tried to tell us that it was because the car was a turbo. We weren't buying it and told them we wanted it looked at. After brining it into the dealer they mentioned that Mazda had a bulletin for a valve seal fix that might help it stop burning oil. So they admitted that yes it was burning oil. After googling the bulletin I realized that our vehicle is having the same problems that many others with 2021 Mazdas (certain production period) are having. …

1) What component or system failed or malfunctioned: On 6/12/2026 While drive on the highway with our daughter in the car and we experienced a high speed stall. The engine failed and we lost power. We barely got the car of the highway and coasted into a parking lot. 2) Life threating for Father, Mother and daughter and other drivers on the highway. 3) The Mazda dealer stated they were unable to reproduced problem. The diagnostic report showed few random misfired on two cylinders 2 & 3. Autozone detected codes P0300 with Secondary DTCs U0442-00 4) There car was only inspected by the dealer. The vehicle has not been inspected by Mazda the manufacturer. We requested Mazda to escalate this to the District Service Manger and to open hotline call with Mazda corporate but both of these were denied. All our service has been performed at Mazda dealer, including oil changes. …

2021 Mazda CX-9 (VIN: [VIN] / 72,400 mi) Vehicle has suffered complete, sudden loss of motive power at high freeway speeds on four separate occasions. Without warning, the engine loses all propulsion, essentially stalling mid-traffic and forcing me to dangerously coast across active freeway lanes to the shoulder. This creates an extreme risk of a high-speed rear-end collision. No crash or injuries have occurred yet, but the car is entirely unsafe to drive. The authorized Mazda dealership has been completely unable to diagnose or fix this intermittent failure. Due to the persistent danger, the vehicle is currently at the shop with the same problem, where it has been since Oct 8, 2026. This is not an isolated issue. As you will see from the pictures, there are several dates where the same situation has occurred in the vehicle goes into limp mode. …

I purchased this vehicle June 5 2021. The vehicle has approximately 9150 miles at this time. I changed the oil the first time at 3222 miles just because it was new and I wanted to have a starting point on oil changes. The car has an app you load on your cell phone for messages. The first time I received a massage that the engine was low of oil was around 6700 miles. I checked it and it was low with at the add oil mark with 3500 miles driven. I received a second message from the app stating the oil was low. Again, I checked the oil and it was to the add oil level with 9014 miles or only been driven 2300 miles. I have contacted Mazda and will take it to the dealership in a few days, but I am having to add and check the oil ever day or so. There seems to be an oil consumption issue with this engine.

My 2021 Mazda CX-9 uses excessive engine oil as reported in the Mazda "M-Tip" bulletin MT-005/20 and this manufacturer's defect is reportedly caused by defective valve stem seals as claimed in the class action lawsuit U.S. District Court for the Central District of California, Southern Division: [redacted] v. Mazda Motor of America, Inc. The valve stem seal problems allegedly cause excessive oil consumption between regular oil change intervals, which increases the risk of engine damage and failure. I believe Mazda must address this issue as soon as possible and repair my affected vehicle before I suffer catastrophic engine failure or long-term engine damage.

Check engine light comes on and error P0303 comes on. Had an independent mechanic do the following and after each one, error P0303 still came on 1. Swap the ignition coils from 2 to 3 2. Swap spark plugs from 2 to 3 3. Swapped injectors 4. Compression test 5. Leak down test 6. Changed the spark plug, coil and injectors 7. Looked for vacuum leaks. Mechanic believes that it is related to the cracked cylinder head in the recall, MC-10232269-0001.pdf. My vehicle is just outside of the recall range and has 87k miles on it. Other research online shows other people with the same vehicle and similar milealge are also having this problem.

I just purchased this vehicle 2 months ago. Yesterday my oil light came on, I pulled over and checked the oil it was completely low. I had to put a quart of oil in it. After that I did some research and learned this seems to be an issue with some 2021 models the cx9 included. There needs to be a recall on this and Mazda needs to fix this issue. These cars cost way to much to have to put a quart of oil every month.

Engine complaints in other CX-9 years