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

Automatic trunk closing mechanism caused the trunk hood to close on my head as I was putting groceries in the trunk. This has occurred several times in the past but this time it hit my head with more force. I have not brought it to a dealer and it has not been inspected by the manufacturer, police or any other entity. There was no warning or alarm before it closed. This could cause serious head injury to an individual on blood thinners.

NHTSA ODI 11747837

Vehicle has ongoing and recurring electrical and engine-related defects that affect safe operation. The primary systems involved are the electrical system, engine ignition system, and powertrain. The vehicle is available for inspection upon request. Prior service records show issues beginning in 2020 involving repeated electronic system failures requiring multiple repairs and component replacements. Since purchasing the vehicle in April 2023, the vehicle has developed more serious failures, including: – September 2024: Check engine light with loss of power and inability to exceed safe driving speeds – October 2024: Engine misfiring due to ignition coil failure requiring replacement of ignition components – September 2025: Additional ignition coil electrical fault (code P0353) The problem has been reproduced and confirmed through dealership service inspections and diagnostic reports. Warning indicators, including the check engine light, appeared prior to failure events. These defects create a safety risk due to potential loss of power, engine failure, and unreliable vehicle operation while driving, which could increase the risk of an accident. The issues have required multiple repairs without permanent resolution and appear to be ongoing and worsening over time.

NHTSA ODI 11733212

The contact owns a 2020 Mercedes-Benz C300. The contact stated that while at a stop, the vehicle failed to accelerate as intended. There was no warning light illuminated. The dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was made aware of the failure and referred the contact to the NHTSA Hotline to report the failure. The failure mileage was approximately 100,000.

NHTSA ODI 11731613

Car stops accelerating and shifts into neutral without warning I nearly got hit from behind. I have consulted several other Mercedes vehicle owners and all had the same issue. Two of the other owners stated that this happened on the interstate and was very lucky they were not involved in a collision. Both vehicles were GLC 300. Mercedes does not seem to have an answer to the issue and all previous owners traded vehicles for fear of dying.

NHTSA ODI 11729030

I am reporting a catastrophic repeat engine failure on my 2020 Mercedes-Benz C300. On October 9, 2025, with 26,589 miles, the vehicle suffered a Cylinder 2 failure (exhaust valves), causing a dangerous loss of power in traffic. I paid $4,100.43 for a $10,000 plus cylinder head replacement at an authorized dealer (Mercedes-Benz of Atlanta South) on November 13, 2025. Following the repair, the vehicle continued to exhibit multiple 'Check Engine Oil Level' warnings. On February 4, 2026—less than 90 days after the major repair—the engine suffered a total catastrophic failure. The dealer now states the entire engine requires replacement. This repeat failure of a critical engine component at low mileage poses an unreasonable risk of stalling or sudden loss of propulsion on high-speed roads. I am aware of the January 2026 Mercedes-Benz warranty extension (NCU 30-P-072328) for this specific M264 engine defect, which confirms a known manufacturing flaw that the current dealership repair process failed to remediate, leaving me in an unsafe vehicle.

NHTSA ODI 11718583

I purchased this vehicle on December 26, 2025 from an authorized Mercedes-Benz dealership. Shortly after the purchase, I discovered an issue related to the airbag system, which indicates a potential safety defect. At the time of purchase and during the test drive, the vehicle was already turned on, and no warning or disclosure was provided regarding any airbag malfunction or warning message. The issue became apparent only after the purchase. I later brought the vehicle in for repairs. While some repairs were performed, the airbag issue was not fixed and remains in the same condition as before. The dealership is now refusing to repair the airbag system at no cost and is insisting that I pay for the repair, despite the fact that this defect appeared immediately after purchase and was never disclosed to me. I believe this represents a serious safety concern, as a malfunctioning airbag system may fail to protect occupants in the event of an accident. I also believe the vehicle was sold to me with an undisclosed safety defect. I am requesting that this issue be formally reviewed and investigated.

NHTSA ODI 11712823

points: ⸻ While driving, the vehicle displays the warning “Active Brake Assist Functions Limited – See Operator’s Manual.” The message appears during normal driving and does not go away. This warning indicates that the automatic emergency braking / Active Brake Assist system is limited or disabled, reducing a critical safety feature designed to help prevent or mitigate collisions. This creates a safety risk because the vehicle may not automatically brake in an emergency situation. The warning appeared suddenly while driving, with no visible obstructions, weather conditions, or damage to sensors. Restarting the vehicle does not consistently clear the message. The issue has not yet been inspected by a dealer or repair facility. The cause of the malfunction is UNKNOWN, and the vehicle is available for inspection.

NHTSA ODI 11710171

Uneven wear pattern.The wear often occurs on inner shoulder of the tires 5k to9k miles,which can be dangerous tire can wear down to belts on inside edge while the outer tread still looks fine. i have brought this to dealership multiple time with NO FIX but to sale me new tires and alignments.I have spoke to multiple owners of 2020 mercedes c63 and they have the same problem. This is a safety issue and has left my wife and kids on the side of freeway broken down.

NHTSA ODI 11697729

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

BOTH the front tires in my 2020 Mercedes C300 developed sudden belt separation while driving at highway speed this past weekend. These tires were installed by Mercedes of Delray Beach Florida as part of my CPO vehicle purchase in September of 2022 and have less-than 20K miles on them. Tires are Continental ProContact size 225/45 R18 and marked M+S as well as MOE. The vehicle received a routine four-wheel alignment as part of my annual servicing in July 2025 by Mercedes of Fort Pierce, and no indication of any tire issue was mentioned. Tire pressures have been consistently checked monthly and always set cold to 37-PSI specifications. The first indication of a tire issue was a sudden vibration in the steering wheel and I thought I may have lost a wheel weight after driving thru our local car wash the day prior.

NHTSA ODI 11689319

The contact owns a 2020 Mercedes-Benz C300. The contact stated that a section of the roof near the top of the windshield, between the sunroof, had detached and flown off the vehicle while driving 30 MPH in bumper-to-bumper traffic. The driver was able to grab the portion of the rubber gasket and pulled it into the vehicle through the driver’s side front window. The roof was in three pieces. The contact turned on the hazard lights and was able to pull over safely to the side of the roadway. There were no warning lights illuminated. The contact was concerned about the failure potentially causing a road hazard under different circumstances. The vehicle was taken to an independent mechanic the next day who declined to service the vehicle and informed the contact it was an issue for the manufacturer. The contact went to a body shop and was informed that the failure was caused by a design flaw. The contact called the local dealer, who initially did not respond. The contact called the dealer again, who requested photos. The vehicle was taken to the local dealer, who declined the repair the vehicle and escalated the issue. The vehicle was not diagnosed or repaired. The manufacturer was contacted regarding the failure and opened a case, but no decision had been made regarding the repair coverage. The failure mileage was approximately 28,722.

NHTSA ODI 11678311

On Tuesday, June 24th, 2025, the glass panel located between the windshield and sunroof on my 2020 Mercedes-Benz C43 AMG unexpectedly detached and flew off while driving. This posed a serious safety risk to me and others on the road. There were no prior warning lights, messages, or symptoms before the failure occurred. This appears to have resulted from heat stress weakening the bonding that secures the panel to the vehicle—an issue consistent with NHTSA Recall 23V854000. That recall covers my exact year, make, and model, yet my specific VIN has not been included for reasons unknown, despite experiencing the exact same failure described in the recall notice. The issue was confirmed by Mercedes-Benz of Boston, where my vehicle is currently located. The failed component is available for inspection upon request. The dealer quoted me approximately $2,200 for repairs but declined to cover the cost under warranty since my VIN is not part of the active recall. I have opened a case with Mercedes-Benz Corporate to request full or partial reimbursement, and I am reporting this to NHTSA so that my VIN may be considered for inclusion in the recall.

NHTSA ODI 11669230

Over the past month, my 2020 Mercedes-Benz C300 has been experiencing unexpected and increasingly concerning issues with the steering. These problems began suddenly and without any prior warning signs. Initially, the steering has been making grinding sounds more usual, particularly at lower speeds and when making tight turns. Over the following weeks, the issue became more pronounced, with occasional instances of the steering wheel resisting movement or feeling delayed in its response. At times, it feels as if the power steering system is intermittently failing or underperforming. There have been no warning lights on the dashboard, and I have not been involved in any recent accidents or incidents that could have caused physical damage to the steering system. I have maintained the vehicle in accordance with the manufacturer's guidelines, including regular servicing. but there the person before me had been in a accident and it may have been the dealership i bought it off of failed to fix it

NHTSA ODI 11667088

I own a 2020 Mercedes-Benz C300, and the check engine light recently came on. The vehicle has only around 27,000 miles and has been regularly maintained at an authorized dealership. Diagnostic testing revealed fault code P06DA00, indicating an electrical failure or open circuit in the engine oil pump control valve. The dealership confirmed that the valve could not actuate and provided a repair estimate exceeding $7,000 due to the labor-intensive nature of the repair. This issue occurred shortly after the factory warranty expired. The sudden loss of power while driving could pose serious safety risks under different traffic conditions. I believe this may be a manufacturing defect that could potentially affect other vehicles of the same model. This issue occurred shortly after the factory warranty expired. The way the vehicle lost power suddenly while driving could have posed serious safety risks in different traffic conditions. I believe this could be a manufacturing defect and may affect other vehicles of the same model.

NHTSA ODI 11654115

Sunroof is not closing

NHTSA ODI 11647724

THE COMPONENT THAT IS MALFUCTIONING IS THE COVERTABLE TOP OF MY 2020 C300 CABRIOLET MERCESDES BENZ. THE STRINGS/CORDS THAT HOLD THE LINER OF THE COVERTABLE TOP TO THE ROOF ARE BREAKING AND IT MAKES THE COVERTIBLE TOP INOPERABLE. THERE WAS NO WARNING LAMP OR NOTICE OF THIS DEFECT. THERE IS ONLY 11595 MILES ON MY 4 YEAR OLD CAR THAT IS GARAGED. THIS OCCURRED 1 YEAR AFTER MY WARRANTY EXPIRED. THIS WOULD CAUSE THE TOP TO BE STUCK IN THE MIDDLING OF OPENING AND IT COULD NOT BE MOVED MECHANICALLY TO GET IT FULLY OPENED OR CLOSED TO THE WEATHER AND IS UNDRIVABLE.THE COST TO REPAIR IT IS ESTIMATED BY THE DEALER AT $4,000.00. tHE DEALER IS WELL AWARE OF TGIS LATENT DEFECT.

NHTSA ODI 11635599

Roof panel is peeling and rattling loose. I’m afraid it will come off like the other C-300s that were recalled for their roof panel flying off.

NHTSA ODI 11625377

I was driving on the highway, with no other cars near me and my panoramic sunroof exploded. It made a very loud gunshot like sound and I felt shards of glass fall on my head while driving. I had 2 other passengers In the car. One in the passenger set and one in the rear passenger side seat. They both had glass hit them in the face on head and go inside their clothes. I was extremely startled thinking that someone had shot at us or something and had to quickly take a highway exit to pull over and see what happened. Apparently this is a common thing with Mercedes as there is a class action lawsuit relating to this issue.

NHTSA ODI 11622207

My wife was driving our 2020 Mercedes Benz C300 coupe near our house and the engine light came on. Then the car could not be driven over the speed of 30 miles per hour. Then it stopped and had to be towed. Fortunately, she was able to avoid being hit by other vehicles.The car only has 25219 miles. It was towed to a mechanic who performed a diagnostic test which provided a series of codes regarding the malfunction. Three codes were related to the CAMTRONIC camshaft system and its Solenoid ( Codes: P003C-53; P34AE-00; P34AD-09). Camshaft position actuators Failure codes: P34AD; P34AE. The way it happened could have resulted in damage, serious injury or death since the car suddenly stopped. The car is well maintained. We believe that there is a manufacturer's defect since this is a garaged vehicle that is well maintained and has low mileage.

NHTSA ODI 11589214

Cylinder head is defective. Service advisor told me it was a known issue in which exhaust valves within cylinder head are prone to premature wear. If left unaddressed it leads to inevitable engine failure. I was quoted $12,000. My car is 2020 model year with not even 60,000. Barely even 4 years old.

NHTSA ODI 11580278

The issue is that the trunk lid closes abruptly and unintentionally. On Saturday, February 3, 2024, as I was putting a shopping bag in the trunk of my car, the trunk lid closed abruptly without my pressing the close button and hit my forehead. The impact was such that my eyeglasses flew off my face and hit the ground. The pain was severe and two days later, I still have pain. While there was no tear to the skin, there's a bump on my forehead and is still painful. The head injuries generally do not show adverse symptoms until months after the incident. I called the Mercedes Benz corporation and after they checked the car VIN, said there had not been any recall for this specific issue. However, searching the internet, there are reports and complaints about this exact defect.

NHTSA ODI 11569947

The car will randomly go into a neutral condition while driving the car. This occurs about once per month, sometimes more often. I will come to a stop for a light or stop sign, upon green light I release the brakes and then gas only to find the engine free revving and the car will not move. I must place the car in Park and then Drive again in order for it to move forward. I have brought this up with Mercedes multiple times and eventually had the transmission replaced. 2 days later, the same thing happened. They do not have a repair available and are dragging their feet to fix. There is a systemic defect in the 9G tiptronic transmission. There are other reports of this transmission going into a "neutral" condition. With the C43 being a relatively lower production class in the C class lineup, I suspect the issue has not made the attention that a higher production vehicle would. I have video with the car 'in gear' and not able to move. And video evidence of the of the transmission glitch.

NHTSA ODI 11533418

This has happened a couple of times to me so far. I have been driving down the road (today it was the highway) and my car fell out of gear into neutral and would not go back into gear unless I restarted the car. Every time it has happened, I have had to coast it to a safe spot to restart the car to get it back into gear. Not having power and needing to coast it to safety is a risk to others because I have no control to get myself to safety in some situations. No dealer has been able to reproduce it because of how infrequently it happens. It has happened 3 or 4 times in the last 15k miles. There were no warning messages or indications that it happened or was going to happen and no parts have been inspected. It is really scary when it happens and I hope it dosen't happen to anyone else.

NHTSA ODI 11527655

The contact owns a 2020 Mercedes-Benz C300. The contact stated while driving 55 MPH, the sunroof exploded without impact and glass fragments fell inside on the rear seats of the vehicle. The vehicle was taken to the dealer and the contact was informed that the sunroof needed to be replaced. The vehicle was not repaired. The contact stated that the failure had occurred twice. The manufacturer was contacted and stated that the vehicle was not under recall. No further assistance was provided. The failure mileage was 34,000.

NHTSA ODI 11526868

The contact owns a 2020 Mercedes-Benz AMG C43. The contact stated while driving 65 MPH, the tire pressure warning light illuminated. The contact took the vehicle to a tire center and was informed that the front passenger’s side rim cracked, causing the tire to deflate. The tire center repaired the original rim. The failure recurred with the rear driver’s and rear passenger’s side rims. The contact stated that the wheels were the original wheels on the vehicle. The vehicle was not diagnosed after the most recent failure. A dealer was not contacted. The manufacturer had not been informed of the failure. The failure mileage was unknown.

NHTSA ODI 11522258