2018 Mazda Mazda6 Powertrain (other) Problems

System Failure: The Power Train (6-speed Automatic Transmission) suffered a major malfunction, documented by diagnostic codes P0731 (Gear 1 Incorrect Ratio) and P0780 (Shift Error). The vehicle is available for inspection. Safety Risk: The failure caused a sudden loss of propulsion while attempting to accelerate. This created an immediate risk of a rear-end collision and left the vehicle unresponsive in the path of oncoming traffic. The transmission's unpredictable shifting makes the vehicle unsafe to operate. Confirmation: The failure and the P0731 code were officially confirmed by Castle Mazda on March 2, 2026. The manufacturer (Mazda) has been notified but has denied a remedy, despite TSB MC-10160555-0001 addressing this specific internal defect. Warning Symptoms: There was no Check Engine Light or dashboard warning prior to or during the failure. The only warning was an extreme, abnormal mechanical grinding/clunking noise from the transmission. The lack of a malfunction indicator light (MIL) meant I had no electronic warning of a looming mechanical failure while in motion.

NHTSA ID

11728615

Incident

Mar 2, 2026

I recently discovered a significant oil leak near the exhaust manifold of my 2018 Mazda 6 (2.5L NA), which has resulted in visible smoke and a burning oil odor. Upon taking the vehicle to the nearest Mazda dealership for a diagnosis, the service department informed me that the vehicle has suffered a cracked cylinder head. An active oil drip is visible behind the engine near the exhaust manifold immediately upon starting the car; consequently, the engine is leaking oil directly onto the exhaust components. This condition not only renders the vehicle inoperable but also presents a significant safety and fire hazard. At the time of this writing, my vehicle has only 46,996 miles and has been meticulously maintained. This mileage is well under the 60,000-mile powertrain threshold and represents a premature failure of a major internal engine component. There are numerous reports on Mazda owner forums describing this identical issue occurring in Mazda 6, CX-5, and CX-9 models. Some owners have even reported instances of minor fires or active burning under the hood due to oil contacting hot engine components. Mazda released Technical Service Bulletin TSB #MC-10241612-0001 (SA-037-23), which includes a redesigned cylinder head for 2018–2020 Mazda 6, 2019 CX-5, and 2016–2020 CX-9 models, demonstrating Mazda’s awareness of this design flaw. While the TSB currently only specifies the 2.5L Turbo engines and not the naturally aspirated variants, there is substantial evidence that this is a widespread defect across these model years, unrelated to owner misuse or vehicle mileage. Mazda should take full responsibility by issuing a formal recall or providing an extended warranty to cover naturally aspirated engines, thereby addressing this problem and preventing further safety risks.

NHTSA ID

11709431

Incident

Dec 23, 2025

Was driving then car suddenly shut down and all panel lights turned on. The car would not start after an hour it started but was Perkins when driving. Mechanics were unable to diagnose the issue.

NHTSA ID

11688263

Incident

Jul 25, 2025

Noticed slight coolant leak, took car to mechanic, he stated cylinder head was cracked, & causing coolant to spray everywhere. Towed car to dealer. Was given repair estimate of over $11,000, for a new engine. I see a safety bulletin online for my year make & model car. This overheating can apparently cause an engine fire. So far, Mazda seems to be showing negligence & not properly addressing the issue for owners.

NHTSA ID

11581010

Incident

Mar 22, 2024

The contact owns a 2018 Mazda Mazda6. The contact stated that he had experienced a transmission surged on five separate occasions since owning the vehicle. There were no warning lights illuminated. The contact had taken the vehicle to the dealer after each failure and various unknown repairs and software updates were performed on the vehicle. However, the failure persisted after each visit. The manufacturer was notified of the failure and a case was opened. The vehicle was not repaired. The failure mileage was approximately 10,000.

NHTSA ID

11478968

Incident

Jul 1, 2020

Mileage

10,000 mi

I took my car in for scheduled maintenance and the technicians at the Mazda dealer found out the tensioner and belt needed to be replaced, when the car is less than 36k in miles. Vehicles being repaired under warranty but a tensioner should not be going out this early in the lifespan of a 2 year old car. I have found a lot of people are complaining for the same issue. This can cause the cars to not run as there’s no notice ahead of time that the belt and tensioner are bad. I do have paper work stating tensioner problems. Vehicles should be recalled due to poor manufacturing and parts making it unsafe on the road.

NHTSA ID

11423596

Incident

Jun 28, 2021

THE FRONT AND REAR SUSPENSION POPS, CLUNKS, THE VEHICLE SHAKES, VIBRATION ALSO HAPPENS, IT ALSO CAUSING TIRES TO BE REPLACED FASTER THAN NORMAL THEY GO BOLD IN THE CENTER ITS CAUSING NOW THE AXLES TO SHAKE AT NIGHT TIME YOU CAN SEE THE REFLECTION FROM HEADLIGHTS BOUNCING, THEY HAVE TSB'S ON THIS SUSPENSION ISSUE HOWEVER NOT FOR 2018 ONLY 14-16 MAZDA 6S I BELIEVE AND SUPPOSEDLY THE ISSUE WAS CORRECTED WELL THEY LIED BECAUSE MINE IS A 18 AND IT IS A DISASTER, MY TRANSMISSION IS NOW SHIFTING VERY HARD FROM 1ST TO SECOND GEAR, TURN WHEEL IT MAKES A LOUD CLUNK SOUND OR POPPING SOUND, GO OVER A DIP IN ROAD DOES THE SAME THING, YOU GO OVER A BUMP THE VEHICLE FEELS SOGGY, IT LIKE DRIBBLES, IT CAUSES THE VEHICLE TO SWAY.. IT'S HORRIBLE, ALSO THE BRAKES WAS SHAKING AT 15K MILES, FOUND OUT IT'S TSBS ON THIS ISSUE AND OF COURSE THE DEALERSHIP DIDN'T FIX FOR FREE, CHARGED ME OVER 600 DOLLARS FOR A ISSUE THAT HAS A TSB ON.

NHTSA ID

11405090

Incident

Mar 5, 2019

Mileage

400 mi

I GOT THIS CAR IN MAY OF 2019 SO THE CAR IS STILL NEW AND EVER SINCE I PURCHASED THE VEHICLE I'VE BEEN HAVING ISSUES WITH IT FIRST WERE THE CALIPERS STICKING AND MAZDA GAVE ME A HARD TIME TO REPAIR THE ISSUE AFTER THE FACT KNOWING THAT IT WAS A MANUFACTURING ISSSUE AND STILL TRIED TO CHARGE ME I TOOK MY VEHICLE THERE MORE THEN 15 TIMES JUST TO DEAL THINGS GOING BAD IN MY CAR. MY CAR STALLS ON ME OUT OF NO WHERE WHEN I'M DRIVING WHICH IS DANGEROUS AND CAN CAUSE ME TO CRASH ALSO MY CAR BRAKES WHEN THERE ISN'T ANYTHING IN FRONT OF IT ALL MY MALFUNCTIONING INDICATORS ARE ON AND I HAVE VIDEO PROOF AND SHOWED IT TO MY SERVICE ADVISOR AND SERVICE MANAGER AND THEY STILL DIDN'T REPAIR MY CAR AND TOLD ME THAT I HAVE TO PAY OR GO SOMEWHERE ELSE ALSO MY SUSPENSION IS MAKING NOISES THEY DIDN'T WANT TO FIX IT AND AS WELL AS MY TIRES PEELING OFF FROM THE SUN ALREADY AND THEY SAY IT'S WEAR AND TEAR AND ASK ME FOR MONEY ALSO MY CAR DIES EVERYTIME I TURN IT OFF I HAVE TO EITHER GET A JUMP OR CALL ROADSIDE FOR ASSISTANCE I'VE BEEN DEALING WITH ISSUES WITH THIS CAR AND MAZDA CLEARLY DOESN'T CARE ABOUT THERE CUSTOMERS SAFETY AND ALWAYS ASK FOR MONEY WHEN THE VEHICLE IS STILL UNDER WARRANTY VERY DISAPPOINTED I'M STILL DRIVING THE CAR WITH ALL THE. ISSUES IT WAS BECAUSE MAZDA WON'T REPAIR MY CAR AND ALWAYS TRY TO PIN THE ISSUE ON ME WHEN KNOWING THAT IT'S THERE FAULT I TOOK IT TO MAZDA SEVERAL TIMES AND NOTIFIED THEM ON WHAT'S WRONG WITH MY CAR AND MY CAR STAYED THERE FOR 4 DAYS AND THEY DID NOTHING TO MY CAR JUST SITTING THERE FOR NOTHING I PAY TOO MUCH MONEY A MONTH AND FEEL LIKE IT'S FOR NO REASON BECAUSE MY SAFETY IS AT RISK I HATE DRIVING MY CAR BECAUSE I FEEL UNSAFE AND SCARED AND GOING TO MAZDA IS POINTLESS PLEASE HELP ME ON WHAT TO DO THANKS

NHTSA ID

11311402

Incident

Sep 11, 2019

Mileage

11,000 mi

VEHIXLE HAS OPEN RECALL #3719F. TOOK VEHICLE IN FOR SERVICE ON JULY 15 AND ACCORDING TO NHTSA RECALL HAS EVEN OUT SINCE JUNE 27.2019. TO THIS DAY I HAVE NOT GOTTEN ANY LETTER OR ANYTHING STATING CAR HAS OPEN RECALL WHEN THE CAR CAN TURN OF RANDOMLY. WILL BE TAKING CAR IN ON 08/26/19 BUT I'M CONCERNED AS TO WHY THIS HAS NOT BEEN ADDRESSED IN ANY LETTERS OR EMAILS

NHTSA ID

11246313

Incident

Aug 23, 2019

Mileage

7,200 mi