What 45 owners told NHTSA about the 2020 Mercedes-benz C-class Cabriolet

I purchased this 2020 Mercedes-Benz C300 only two months ago and have driven it less than 3,000 miles. The Carfax report shows consistent maintenance and regular service history by prior owners. While driving, the check engine light came on and the vehicle began shaking and running roughly. Diagnostics by Peachtree Imports (10/03/2025) and later by Mercedes-Benz of Atlanta South confirmed Cylinder #2 failure on the M264 2.0L engine at only 26,589 miles. The dealer’s report states: “Cylinder #2 mixture formation out of spec. Fault occurred due to worn exhaust valve seat. Cylinder head replacement required.” Estimated repair cost: $10,470.66. This causes misfire, loss of power, and unsafe drivability. The failure matches Mercedes-Benz Technical Service Bulletin LI01.30-P-072328 (2021), which documents valve-seat leakage in M264 engines requiring head replacement. The vehicle is outside warranty but has extremely low mileage, and MBUSA Case #18392667 remains unresolved. It is also important to note that the M260 engine, which is mechanically identical to the M264 but mounted transversely, has already received a warranty extension from Mercedes-Benz for the same cylinder-head and valve-seat defect. This indicates a systemic issue across both engine families, presenting a safety risk of sudden power loss or engine stall during operation.

NHTSA ODI 11695702

CEL with multiple cylinder misfires. Oil leak on top side of engine bank 2 in valley of injectors. Multiple codes for turbo charger faults and also clogged catalytic converters. Dealer confirmed and manufacturer denied federal emissions warranty on vehicle. Due to a modification that plays no role in the power train.

NHTSA ODI 11497171

The component that failed was the fuel injector and spark plug. A few months prior to this incident, I was making a left hand turn, when the accelerator completely gave out. I was making the left on a blinking yellow arrow, luckily the on coming car was not coming at me fast or I would've been in an accident due to the accelerator failing. I had to pull over, turn the car off and then back on to reset it. I was told by the dealership service center that they could not find anything and that there have been no complaints or recalls. After about 8 months of owning the vehicle, it started to have problems turning over when the engine on/off button was pressed. I was repeatedly told that they could not do anything if it did not happen in the dealership service center. This past week on 10/20/2022, while I was driving down the freeway, when I went to accelerate and at that moment the vehicle began to stutter/shake uncontrollably. After that, any time the accelerator was pressed it would shutter/shake. My vehicle was towed to a dealership. Come to find out, cylinder one was coding. They found out that the fuel injector was stuck open. According to the service advisor, that issue was causing a misfire. I was told that they replaced the fuel injector and the spark plug. According to the vehicle report I was given, 1 reman injector, 4 TS spring F In, 1 spark plug, and there was a core return (not sure what that means). The check engine light came on right away. In addition to the incidents above, I have had the forward collision alert come on when nothing is in front of me. I worry that one day it will cause my vehicle to engage the brakes when nothing is around.

NHTSA ODI 11490902

THE FUEL SMELL IS COMING FROM THE RUBBER FUEL, THEY ARE NOT COVER BY MY CPO- WARRANTY ( 3000 USD PAID PACKAGE). I FOUND OVER 100 FRIENDS ON FACEBOOK GROUP HAS THE SAME PROBLEMS. DEALLER REFUSE TO COVER. MY KID IS FELL BAD ABOUT THE SMELL LEAKING.

NHTSA ODI 11390106