Multiple fixes and repairs on a P0421 code. Repaired by Mazda with a new catalytic converter but then refused to replace it when the code came back saying it was not covered by the warranty. Mazda says it is not a common issue but they have had issues in the past with the same P0421 code repeatedly showing up on a healthy car.
Engine & cooling
Mazda CX-30 Engine problems by year
69 complaints filed with NHTSA about the Mazda CX-30's engine & cooling. Stalling, loss of power, oil consumption, overheating, head gaskets, timing chains and engine failure.
Engine complaints by model year
Latest CX-30 engine complaints
I am writing regarding my 2025 Mazda CX-30, purchased brand new with 0 miles on [[redacted]]. The vehicle currently has 22,000 miles. I am extremely concerned about the reliability and, most importantly, the SAFETY of this vehicle. August 29, 2025: I brought the vehicle to the dealership after receiving a recall notice. My service slip states only "performed Software update," with no details regarding the recall. Refers something about the engine being left on over 2 hours will loose power. Mileage was 9,650. ...
Read the full complaint
[[redacted]]: The check engine light came on. I was told the vehicle was leaking oil and that it was not a major concern per a 20year old technician. The dealership replaced the REP Tensioner Belt. [[redacted]]: While driving on [[redacted]] on my way to [[redacted]], my vehicle SUDDENLY LOST POWER AND DIED WHILE I WAS DRIVING. This was an EXTREMELY SERIOUS AND POTENTIALLY LIFE-THREATENING SAFETY INCIDENT. Thankfully, I had not yet entered [[redacted]] and was not hit by another vehicle. Had my vehicle suddenly died after entering [[redacted]], I truly believe the outcome could have been catastrophic or fatal. I DO NOT FEEL SAFE DRIVING THIS VEHICLE! I cannot trust a vehicle that unexpectedly loses power and dies while being operated. This incident has completely destroyed my confidence in the safety and reliability of my Mazda. I am formally requesting that Mazda immediately open and begin the Florida Lemon Law/warranty process, thoroughly investigate the cause of this dangerous loss of power, and provide me with a written explanation of what caused the vehicle to die and whether it is safe to operate. Please treat this as an URGENT SAFETY CONCERN and provide an immediate response. Thank you. [[redacted]] "[[redacted]]" Livingston INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
I was driving my 2026 Mazda CX-30 in a parking lot and was pulling into a parking space at a very low speed. I lightly pressed the accelerator to move the car forward, but the car suddenly surged forward much faster than I intended or expected based on how lightly I had pressed the pedal. The sudden acceleration resulted in a collision and property damage. There were no warning lights, warning messages, or other dashboard alerts before or at the time of the incident. I do not know what specifically caused the car...
Read the full complaint
to accelerate this way. I am concerned that there may have been an issue with the accelerator/throttle response, engine controls, transmission, PCM, or another part of the powertrain. The vehicle has not yet been inspected by Mazda or an independent engineer specifically for this issue, so the cause has not been determined. It is currently as a collision center. Before the accident, I had also noticed that the vehicle's acceleration and pickup sometimes did not feel normal, although there were no warning lights or messages indicating a problem. I am reporting this because the car's unexpected acceleration at such a low speed created a serious safety concern. I would like the incident and vehicle to be investigated to determine whether a defect or malfunction contributed to the sudden acceleration. The vehicle is available for inspection.
Excessive oil consumption. Regularly have a low oil warning come up about 6000 kms after an oil change. Oil is always low when checked.
The contact owns a 2023 Mazda. The contact stated that the vehicle was braking randomly while driving. There was an unknown malfunction code that flashed quickly. The steering was stiff and failed to turn. The steering wheel adjusted and guided the vehicle into the wrong lane. The RPM was sporadically reeving. The RPM increased, and the vehicle stalled without acceleration. There was smoke emerging from the hood. There was oil leaking. The vehicle failed to turn off and on. The fuel gauge and infotainment center...
Read the full complaint
were not working properly. The contact stated that while leaving the local dealer, the vehicle stalled. The battery was replaced. The vehicle was towed to another unknown local dealer who determined the battery needed to be replaced. The vehicle was replaced, but the failure recurred. The dealer determined that there was an oil leak and needed to replace the transmission, serpentine belt, and battery. The dealer informed me additional testing was needed. The vehicle was not repaired. The manufacturer was contacted regarding a buyback, but no assistance was provided. The failure mileage was approximately 37,000.
While driving, on approach to a stop signal, at an intersection the car stopped moving. The display said engine malfunction, have inspected. The electronics and engine continued to operate, but the car would not move when gas pedal was depressed. I shut off and restarted my vehicle numerous times, with no effect on the problem, the car still would not move. The vehicle behind me had to brake unexpectedly, and I could have been hit by others in the intersection, there could have been an accident.(I put car in...
Read the full complaint
neutral and the driver behind me, pushed my vehicle, manually, out of the intersection) AAA towed vehicle to the dealer I purchased it from, they were unable to reproduce the problem or retrieve codes to identify problem.( AAA did something under the hood before towing and I was able to drive vehicle to nearby parking lot to be towed) No other inspection has been conducted. Over prior week I noted intermittent engine revving while driving for very brief seconds and this occurred just prior to the incident that resulted in the inability to move the vehicle.
One day after oil and filter change, engine LOW OIL LEVEL light illuminated on dash. Engine oil dipstick displays full oil level; no signs on oil leaks under the vehicle. Appears to be failed oil level sensor. Upon restarting the vehicle, LOW OIL LEVEL light is turned off. Intermittently returns after some time of driving. Have not observed light turning itself off without shutting down the vehicle.
I wondered if, after my first service visit on 11-12-25, the dealership put regular leaded gas instead of premium in it, because there was a noticeable difference in gas mileage and the engine started revving pretty high, in my opinion. It also seemed to have less power (which was my main reason foe thinking the wrong gas had been out in). And since then, it hasn't been the same.
At around 26,528 miles my 2022 CX-30 2.5s (not the turbo) developed a "Low Oil Pressure" warning while driving between 55-65mph on 07/06/2025. The car has had regular oil and filter changes about every 5K miles. The last oil and filter change was at 25,259 mileage on 05/25/2025. There aren't any visible oil leaks. I have read that this is a common problem for other Mazda CX-30 years 2021- 2022.
As reported by others, Engine Malfunction light came on. Car running rough. Mazda dealer says corroded wiring harness and $5k to replace. They bypass the conventional repair and splice it in. Within a hour of driving after pick up, same engine malfunction light and rough running returns. This time they said I need a new transmission. Electrical issues and faulty transmission are both dangerous. With as much posted online regarding the transmission, I would hope to find a recall. $10k in repairs for a barely 4 yr old car!
Received a "LOW ENGINE OIL LEVEL" warning message before the regular oil change interval of 7,500. Light came on 11/20/24 after purchasing the vehicle from a Mazda dealership 8/10/24 (~3 months). Model and VIN were impacted by the Mazda Valve Stem Seal Settlement. This issue was not disclosed by the dealer.
Low Engine Oil Light keeps appearing at seemingly random intervals. I will heat up my vehicle, begin driving, and sometimes after 10 minutes, sometimes after 20 minutes it will come on. I drove 2.5 hours and it did not come on at all. It first started Friday 11/29 and was driven to and from a few places and came on 50% of the time. The 2.5 hour drive occurred on Saturday 11/30 and the light did not come on at all.
The contact owns a 2021 Mazda CX-30. The contact stated while driving 65 MPH, the vehicle stalled. The messages "Engine Malfunction" and "Computer System Issues" were displayed. The contact was able to pull over to the side of the road. Another driver assisted the contact in jumpstarting the vehicle. The contact was able to drive to her friend's residence. The contact then drove to her residence the following day. The contact stated while starting the vehicle, the vehicle jerked and the failure recurred. An unknown...
Read the full complaint
dealer was notified of the failure and provided an estimate for a diagnostic test. The vehicle was not diagnosed or repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 30,590.
While I was driving on I-90, I lost control of the acceleration of my vehicle. The vehicle was towed and has been diagnosed with a failed transmission! The car would not accelerate or it would accelerate in bursts or rapidly slow down. I was able to pull over and the car failed to move at all after. My safety and others was put at risk as I lost the ability to control the speed of the vehicle on a road where the speed limit is 65mph in traffic around me. When the problem began no lights illuminated, until ~30...
Read the full complaint
seconds in the yellow engine failure light illuminated and then the yellow transmission failure light illuminated. The car was brought to a dealership for inspection and they diagnosed it as a transmission failure. This is unacceptable for such a young vehicle (2021). It should be noted that the car manufacturer immediately approved the replacement the same day it was diagnosed (dealership said it usually takes 48 hours), but the part is back-ordered for months (probably because they know this is happening and trying to cover it up).
My oil changes were affected as well.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) complaints and recalls, checked daily. Complaints are owners' own reports and are not verified. How we use the data