What 24 owners told NHTSA about the 2023 Mercedes-benz C-class Cabriolet

I am filing a safety complaint regarding my 2023 Mercedes-Benz AMG C43 4MATIC. The vehicle has approximately 23,000 miles. On multiple occasions, the vehicle has abruptly and violently applied the brakes and/or come to a near stop while I was driving on highways and side roads, even though there was nothing in front of me that should have triggered emergency braking. There was no vehicle, pedestrian, cyclist, object, or road hazard present that would justify this braking event. This is not normal braking behavior. The car essentially performs an uncommanded emergency stop or severe deceleration without warning. The force is strong enough to create a serious risk of being rear-ended by vehicles behind me. This has happened at highway speeds and on local roads, making the vehicle unsafe to operate. If a following driver is unable to react in time, this defect could easily cause a crash, injury, or death. The problem appears related to the vehicle’s automatic emergency braking / Active Brake Assist / forward collision avoidance system and possibly other linked driver-assistance systems. The vehicle has already been serviced on two separate occasions for this exact issue, yet the problem has occurred again. Despite bringing the vehicle in for repair more than once, the defect remains unresolved. Because this dangerous unintended braking continues to happen, I cannot continue to drive the car safely with this issue unresolved. On April 1, 2025, I took the vehicle to Aristocrat Motors in Merriam, Kansas for the car slamming on the brakes and beeping when no one was around. The service center calibrated the augmented reality camera and performed a test drive. The invoice indicates that they were unable to duplicate the braking event during the test drive. They ran codes with SDS and found that the augmented reality camera was not calibrated correctly, so they performed a calibration. On December 31, 2025, I again took the vehicle to Aristocrat Motors in Merriam, Kansa

NHTSA ODI 11735812

The contact owns a 2023 Mercedes-Benz C300. The contact stated that on occasion while driving at various speeds, the vehicle unexpectedly stopped without the brake pedal being depressed. There were no warning lights illuminated. The vehicle was diagnosed twice by the local dealer, and the contact was advised that the Forward Collision Avoidance sensors needed to be recalibrated; however, the failure persisted. The vehicle was taken back to the same dealer where the vehicle was inspected, and the contact was advised that further diagnostic tests were required to determine the cause of the failure. The vehicle was not repaired. The manufacturer was not notified of the failure. The approximate failure mileage was 28,000. The VIN was not available.

NHTSA ODI 11680376

On 4 different occasions car brake assist activated causing car to come to an immediate stop and jerk. At stop light as I started to accelerate a left turn car came to an immediate stop almost causing the car behind hit rear end. Brake assist light activated. This happened twice. And twice when in reverse backing out of a parking space and backing into driveway. Dealership notified look at my car and stated they did not see anything wrong. 4th incident happened within 30 minutes after leaving Wilmington Mercedes Benz.

NHTSA ODI 11674663

This car has the driver assistance package including Active Speed Limit Assist which is supposed to automatically adjust the speed of the vehicle based on detected speed limits. However, it gets the speed limit wrong an excessive amount of the time sometimes resulting in the car suddenly decelerating which I consider to be a serious safety issue that could result in collisions. In my situation, I have experienced the car suddenly slowing to 40 mph for no reason in an area where the speed limit was 65 mph. I have also seen this problem documented on a number of blogs related to Mercedes-Benz vehicles. When I reported the problem to the dealership, I was told that it was a known issue and was encouraged to turn this feature off. I think Mercedes-Benz needs to fix this known issue for those of us who have cars with Active Speed Limit Assist.

NHTSA ODI 11612912

Filing complaint on behalf of my sister. She was driving on empty side street around 25mph and the car comes to an abrupt stop. Apparently part of the collision avoidance system, yet nothing in road, on road or in sight. If there was anyone behind her, they would have slammed into the rear end of her car.

NHTSA ODI 11584616

The contact owns a 2023 Mercedes-Benz C300. The contact stated that while driving with the Adaptive Cruise Control engaged, the vehicle decelerated quickly, causing the driver to lose control of the vehicle. The vehicle was not diagnosed or repaired by an independent mechanic or dealer. The manufacturer was not made aware of the failure. The failure mileage was unknown.

NHTSA ODI 11580656

The contact owns a 2023 Mercedes-Benz C300. The contact stated while driving 50 MPH with the Intelligent Cruise Control activated, with no other vehicles or objects nearby, the vehicle inadvertently slowed down. After restarting the vehicle, the vehicle returned to normal functionality but later displayed the following messages: “Active Emergency Stop Assist Currently Unavailable”, and “Active Steering Assist Inoperable”. The Forward Collision Avoidance warning light was illuminated. The vehicle was taken to the dealer but not yet diagnosed. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was 6,000.

NHTSA ODI 11544088

Major safety issue - PHANTOM BRAKING. On 2 separate occasions the vehicle engaged emergency braking while there was no apparent hazard. This phantom braking was very dangerous. This car has adaptive cruise control. It occurred in the exact same spot on Interstate-84 and NE 21st Avenue in Portland, Oregon while traveling east bound. The cruise control was on and engaged in incident 1. Cruise control was on, but not set, in the second incident. First incident was approximately 6/1/23. Second incident was 7/16/23. I have reported to Mercedes Benz Customer service. Case opened #2-42097036640. I will contact the dealership to report as well.

NHTSA ODI 11532743

The Mercedes just slams on the brakes for no reason. It's happened 3x and is very scary. According to Internet posts this is a common problem because of collision assist malfunction

NHTSA ODI 11528225

- December 5, 2022, while driving on I-20 East in Atlanta, Georgia in the evening, at a speed of 15-20 mph my vehicle abruptly came to a stop in the middle of traffic with no warning and no action prompted by me while driving. There were vehicles positioned in front and behind my vehicle. Thankfully, the vehicle behind me was able to slam on its breaks to prevent colliding into my vehicle. - April 7, 2023, while driving in southwest Atlanta in a residential area at a speed of 15-20 mph, while on the phone with one of my work colleagues, my vehicle abruptly stopped while driving past houses with no warning and no action prompted by me while driving. There was a vehicle positioned behind me that was able to slam on its breaks to prevent colliding into my vehicle. - May 5, 2023, while driving in a residential neighborhood on W Wesley Rd in Atlanta at a speed of 10-15 mph in a construction zone, my vehicle again abruptly stopped with no warning. This time, the stop was much more forceful than previous incidents. - May 5, 2023 my car received the following prompt on my screen "Your vehicle has detected a breakdown. Do you want to receive support from Mercedes-Benz Roadside Assistance" - Mercedes assessed my car and reported the following: C111A00 Radar sensor 1 is disrupted by interference from an external transmitter." Then, "NOTE PER OWNERS MANUAL, THE SYSTEM ON THE CAR CANNOT ALWAYS TAKE INTO ACCOUNT ROAD, WEATHER OR TRAFFIC CONDITIONS///BE AWARE OF THE LIMITATIONS REGARDING THE SAFE USE OF THE THESE SYSTEMS///" - The vehicle does not send an alert, forewarn, nor does it allow you to override an automatic emergency break - Mercedes Benz was flippant, dismissive and asked me to resume driving in an unsafe vehicle. I am filing this because they appear to have no regard for human life. I fear for my life and do not want to pass this burden on to someone else -In every instance described above, I contacted Mercedes Benz to make them aware. The contact is requesting to rescind the complaint and does not wish to move forward with the claim.

NHTSA ODI 11524034

The contact owns a 2023 Mercedes-Benz C300. The contact stated that while driving at various speeds, the Forward Collision Avoidance system erroneously activated, causing the vehicle to abruptly stop in the middle of the road. The failure occurred on three separate occasions and each time no other vehicle or object was nearby to cause the Forward Collision Avoidance system to become activated. The vehicle was taken to the local dealer who replaced sensors and recalibrated the Forward Collision Avoidance system, but the failure persisted. The manufacturer was not notified of the failure. The failure mileage was 1,000.

NHTSA ODI 11520487