2021 Mazda CX-9 problems

Filed Nov 4, 2026 · Engine · 86,000 miles · NJ

The contact owns a 2021 Mazda CX-9. The contact stated that while driving approximately 20 - 25 MPH, the check engine warning light illuminated. The contact used a diagnostic scanner and retrieved DTC: P0303, for a cylinder #3 misfire. The vehicle was taken to a local Mazda dealer to be diagnosed and repaired. The dealer found a coolant leak and performed a system cleaning and replaced the spark plugs and fuel injectors. However, the failure reoccurred. While the contact's wife was driving the vehicle, the check engine warning light illuminated, and the vehicle was towed to the dealer by the insurance company. The contact requested that the dealer inspect the cylinder head gasket and coolant system in his presence. The dealer informed the contact that the repair warranty would be limited to one year or 12,000 miles. The contact also contacted the manufacturer customer service but was not provided any additional assistance. The failure mileage was approximately 86,000.

Filed Oct 14, 2026 · Electrical, Engine · CA

2021 Mazda CX-9 (VIN: JM3TCBDY3M0538768 / 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. Mazda corporate has been contacted case 00503976. I am requesting a buyback. I request an urgent the federal safety agency investigation into 2021 CX-9 power loss defects for a potential recall.

Filed Sep 12, 2026 · Acceleration, Driver assistance · TX

I entered the interstate normally, with no issues accelerating or merging. While driving at approximately 70 mph, in traffic, all three warning messages appeared on the instrument cluster at the same time: “Smart Brake System Malfunction,” “Driver Attention Alert System Malfunction,” and “Forward Smart City Brake Support Malfunction.” At the same moment, the vehicle began to lose speed. I pressed the accelerator pedal firmly. The speed continued to decrease instead of increasing. I could not accelerate at all. An exit was thankfully immediately available. I took the exit, then continued on a side road, then into a parking lot before I could find a safe place to stop. At no point did the pedal work again — I was immensely lucky to navigate safely, especially with my toddler in back seat. Other traffic was present on the interstate at the time. The sudden loss of throttle at that speed, with traffic present on each road and merging across numerous lanes in [XXX] traffic, created a serious risk of collision while I searched for a safe stop. The vehicle has not been inspected by a dealer, it’s with Hiley Mazda of Hurst dealership in [XXX] now. TBD whether the problem can be reproduced. The vehicle can be available for inspection if needed. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 27, 2026 · Tires · IL

On a high-speed highway (Route 14), the vehicle suffered a sudden flat tire/air loss event, forcing an emergency pull-off onto a narrow shoulder with 65 mph traffic. Subsequent inspection revealed the failed tire and the rest of the set were manufactured in late 2007 (DOT code 4907). These 19-year-old tires were installed by a professional tire shop despite being far beyond their safe service life. Component/System Failed: Tires (Set of 4). Tire Size: 255/50 R20 (Vredestein Wintrac 4 Xtreme, DOT 4907). Available for inspection upon request. Safety Risk: Sudden tire failure at highway speeds created immediate loss-of-control risks and exposed occupants to high-speed semi-truck traffic on a narrow shoulder. Confirmation/Inspection: DOT date code 4907 confirmed by visual inspection. The installing tire shop was notified and acknowledged the sale/installation. Not yet inspected by manufacturer or law enforcement. Warning Signs: No warning lights, pressure drops, or symptoms occurred prior to failure. UNKNOWN if internal tread separation preceded deflation.

Filed Aug 10, 2026 · Acceleration, Engine · IA · crash

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.

Filed Jul 23, 2026 · Engine · RI

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. We have always received a video of them working on our car with a detailed summary of what done. We did not receive the video or diagnostic report for this issue. 5) There were no warning lamps, no messages or other symptoms of the problem prior to the failure.

Filed Jul 12, 2026 · Engine · VA

This complaint refers to Mazda and it's dealer refusal to properly execute the warranty work under the SSPD5 Valve Stem Seal Class Action Campaign and does not follow the Court's approval of the final Settlement Agreement. I assert that Mazda and it's dealer are not following the SSPD5 repair procedures. 1. I have documentation and complaints going back to Dec-2023 with this particular dealer that I have experienced low level oil consumption within the 7,500 mile oil change interval. The dealer did not detect oil leaks in any of the engine systems. 2. I presented the vehicle to the dealer with the Engine Oil Level Warning Light illuminated. The Diagnostic Trouble Code (DTC) P250FF:00 should be stored in the vehicle memory. 3. The vehicle had 50,501 miles and was within the original 60 month limited powertrain warranty. 4. The dealer refused to conduct the valve stem seal repairs until an oil consumption test was run. The dealer claims that because I had another service center (note that I use full synthettic oil that meets Mazda oil specifications) conduct the most recent oil change at 43,738 miles (note within the 7,500 oil change interval and the 1 year time window) that the dealer would require an oil consumption test. I assert that this is not required per the class settlement agreement and the SSPD5 repair procedures that Mazda sends to all of its dealers. 5. I researched the available documentation that it's available through the The language in these documents is very clear. 6. SSPD5 Valve Stem Class Action Campaign, Repair Procedure 6-12-2024: a. "The DTC250 is not required to be present for valve stem replacement." b. "Customer complaint of oil consumption...OR Low Oil Light OR DTC250 follow the flow chart." c. Flow chart says "Replace the exhaust valve stem seals by following TSB 01-003/24" if no previous warranty work done. 7. SSPD5 updates on 8-6-25 and 4-28-26: a. Refer to page 4, DTC250 is NOT required to be presented (it is noted in RED).

Filed Jun 18, 2026 · Engine · MA

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.

Filed Dec 10, 2025 · Driver assistance · AZ · crash

Backup camera shows three to four feet before red collision line is not accurate causing severe damage to my garage door.

Filed Jun 5, 2025 · Transmission · GA

My vehicle is part of Mazda's 2021-2022 Mazda Valve Stem Seal Settlement. The dealership had yet to call me in for the repair of said valve seal repair as I was on a list. The settlement is suppose to extend out the powertrain warranty on the vehicle 2 years/24,000 to 7 years/84,000. My vehicle has 60,083 miles on it. One of the cylinders on my vehicle lost compression. The dealership and Mazda both say they will not cover the cost for repair as they only are covering things in the powertrain relate to oil consumption. The cylinders are part of the powertrain and carbon buildup from excessive oil burning because of the defective seal causes valve damage or sticking which will cause compression loss. Mazda is actively denying what they agreed to in the settlement and costing people money for repairs that should be covered.