2020 Mercedes-Benz C 300 Owner Complaints

I own a 2020 Mercedes-Benz C300 equipped with a power trunk. On July 22, 2026, I took my vehicle to Annapolis Mercedes-Benz because the power trunk was repeatedly closing on its own while people were standing in the trunk opening. I specifically reported that the trunk was unexpectedly closing while I, my child, or another individual was loading or unloading the vehicle and expressed concern that someone could be injured. The dealership kept the vehicle for several hours but advised me that no malfunction could be found. I was told the trunk had been reset and that there were no problems with the vehicle. I also provided video evidence of the trunk malfunction by text message to my service advisor. On August 2, 2026, the exact same problem occurred. While I was loading groceries into the trunk, the power trunk unexpectedly closed without warning and struck my son in the head, causing injury. This incident occurred after I had already reported the same safety concern to the dealership. I believe the power trunk is malfunctioning intermittently and presents a significant safety hazard because it can unexpectedly close on a person while the trunk is being used. I am requesting that NHTSA investigate this potential safety defect, as it may pose a risk of injury to other vehicle owners and passengers.

NHTSA ID

11754327

Incident

Aug 2, 2026

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 ID

11747837

Incident

Jul 1, 2026

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 ID

11733212

Incident

Sep 1, 2024

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 ID

11731613

Incident

Apr 16, 2026

Mileage

100,000 mi

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 ID

11718583

Incident

Oct 9, 2025

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 ID

11712823

Incident

Dec 26, 2025

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 ID

11710171

Incident

Jan 10, 2026

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 ID

11695702

Incident

Oct 3, 2025

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 ID

11689319

Incident

Sep 20, 2025

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 ID

11678311

Incident

Jul 24, 2025

Mileage

28,722 mi

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 ID

11667088

Incident

May 21, 2025

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 ID

11654115

Incident

Mar 27, 2025

Sunroof is not closing

NHTSA ID

11647724

Incident

Mar 11, 2025

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 ID

11635599

Incident

Dec 27, 2024

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 ID

11625377

Incident

Nov 14, 2024

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 ID

11589214

Incident

May 13, 2024

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 ID

11580278

Incident

Mar 16, 2024

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 ID

11569947

Incident

Feb 3, 2024

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 ID

11526868

Incident

Jun 12, 2023

Mileage

34,000 mi

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 ID

11490902

Incident

Oct 20, 2022

The contact owns a 2020 Mercedes-Benz C300. The contact was reversing out of her driveway at 3 MPH, the contact was using her rearview camera. The contact stated that the image froze and she crashed into a parked vehicle with the rear passenger side bumper of her vehicle. The contacts bumper was scratched and dented. The other vehicle had sustained a large dent in the driver’s side door. The contact stated no warning light was illuminated. The contact had taken the vehicle to a local repair and not a dealer or an independent mechanic. The vehicle had been repaired cosmetically. The manufacturer had not been informed of the failure. The contact had received the manufacturer recall letter and related the accident to NHTSA Campaign Number: 22V232000 (Back Over Prevention). The failure mileage was approximately 6500.

NHTSA ID

11475739

Incident

Jul 6, 2022

Mileage

6,500 mi

OEM tires that the Mercedes Benz dealership diagnosed as having shifted belts. 245/40 R18

NHTSA ID

11474717

Incident

Jul 19, 2022

The contact owns a 2020 Mercedes-Benz C300. The contact stated that suddenly the vehicle's sensors were illuminating and activating a warning stated that the sensors were defective. Many of the vehicle's sensors began to deactivate and malfunction. While reversing out of a parking space the rear view camera and sensor system failed causing the contact to crash into another vehicle. Both vehicles were damaged. A police report was filed. There were no injuries reported. The vehicle was not towed. The contact took the vehicle to a repair facility and stated that there was damage to the internal sensor and camera system. The contact took the vehicle to the dealer however the vehicle had not been diagnosed or repaired as of yet. The contact then received a recall notice NHTSA Campaign Number: 22V232000 (BACK OVER PREVENTION) however the VIN tool confirms remedy not yet available. The manufacturer was not made aware of the failure. The approximate failure mileage was 3,000.

NHTSA ID

11469155

Incident

Apr 8, 2022

Mileage

3,000 mi

Automatic emergency braking system & forward collision warning. I experienced a medical emergency and blacked out, hitting 3 cars. The incident happened the morning of Dec. 31, 2021 and my car still has not been evaluated by Mercedes. I was taken to the ER and spent 3 days in the hospital.

NHTSA ID

11452817

Incident

Dec 31, 2021

On July 17, 2021 I was driving at the posted rate of speed down I-275 Southbound here in Michigan. All of the sudden and without warning, there was a loud explosion which happened, from as near as I can tell, in the driver's side windshield pillar, where there is an airbag. No warning lights came on, and the car did not change its driving characteristics. Only after I reached my destination and searched under the dash, and every where else (including the exterior), did I find that the plastic "cover" on the pillar is pushed away from the pillar and much more loose than the plastic cover on the passenger side. Since the incident, I have had severe tinnitus in my left ear which was about 15-18" away from it. The air bag did not deploy. I did not hit a pothole, did not hit a bump, did not hit another vehicle.

NHTSA ID

11428078

Incident

Jul 17, 2021