2021 Mazda 3 Reliability Report

The car fails to stop or surges forward at low speed even with the brake pedal pressed. These reports include 3 crashes, in a parking garage, at a red light, and while shifting from a standstill. No warning light appears beforehand. Automatic emergency braking also slams on with nothing ahead, in one case causing a neck injury. Another driver saw a critical brake system malfunction message that no shop could explain. Dealers report no permanent fix. Rear brakes also wear out unusually fast.

The transmission fails suddenly in some cars. The car surges, accelerates in bursts, or loses power on the highway before engine and transmission warning lights come on. In another case, a rough-running engine was blamed on a corroded wiring harness, and the dealer then called for a new transmission. Other complaints describe the same oil consumption seen under the engine category, with low oil warnings before the scheduled change. Owners cite a valve stem seal settlement and a service bulletin. Battery drain after a new battery, random lock and liftgate behavior, and poor fuel economy also appear.

The car speeds up on its own. Reports include 2 crashes, one into a brick pillar and one into an apartment building, and one caused neck and back injuries. In the second case, pressing the brake did not stop the car while parking. Adaptive cruise control also accelerates hard when the car ahead leaves the lane, briefly going above the set speed. One sudden lunge in a turn was followed by a transmission error and a code for a stuck shift solenoid.

Binding at highway speed, followed by a sudden release, makes small lane corrections jerky and leads to overcorrecting. Owners say the symptoms match a Mazda service bulletin that covers only vehicles through model year 2020. One dealer planned to relubricate the worm gear in the steering assembly. A separate report describes a burst of warnings, including power steering, push button start, and in-vehicle network faults. After that, the car would not start and was towed to a dealer.

Automatic emergency braking engages with nothing ahead. In one case it skidded the car to a stop in a traffic lane after a turn, and the owner later found flies on the front sensor. Rear-end collisions were avoided only because traffic behind was far enough back. In the most serious report, cruise control at 60 mph did not disengage when the driver braked approaching a light. The crash that followed injured 4 people, and no warning light appeared.

In serious side and middle impacts, the bags on the struck side or the front fail to deploy. Both reports involve cars that were totaled. In one, the driver side bags deployed but the struck passenger side bags did not. The passenger suffered shoulder fractures and a broken clavicle. In the other, a car hit the middle of the vehicle during a left turn, no frontal bags deployed, and the driver was severely injured at 13,450 miles. Neither report includes a confirmed fault from a dealer or the manufacturer.

A seatback fold mechanism comes loose at 23,000 miles. In a separate report, the driver seatbelt retractor stops retracting with no dashboard warning, and the owner worries the pretensioner will not work in a crash. With only two complaints, no broad pattern is clear. Both involve parts that matter in a collision, so they are worth checking on any car under consideration.