2024 Mercedes Benz GLC 300 problems

ENGINE

While driving the vehicle the engine started running rough, check engine light illuminated and it would not accelerate above 40 mph. There are 29,100 miles on the vehicle, it's been serviced on schedule by Mercedes and is owned by me since new. It is especially concerning due to the acceleration topic which could have been catastrophic if I were trying to merge into traffic. Dealer service say the camshaft bearing needs to be replaced. It seems this is very premature for the mileage on the vehicle.

NHTSA complaint #11741752 — an unverified report by a vehicle owner.

POWER TRAIN

While driving my 2024 Mercedes-Benz GLC 300 on California highways, the vehicle has repeatedly experienced sudden uncontrolled deceleration, unexpected transmission downshifts into 2nd gear, severe transmission jerking, and complete loss of accelerator response. The first major incident occurred on March 7, 2025, while traveling on Interstate 5 at approximately 70 mph. The transmission suddenly jolted and downshifted directly into 2nd gear. The vehicle immediately lost power and slowed to approximately 20 mph without warning. I exited the highway and restarted the vehicle before it temporarily resumed normal operation. A second major incident occurred on May 7, 2026, while driving on Interstate 5 near Flag City, California at approximately 65 mph. The vehicle suddenly decelerated uncontrollably to approximately 20 mph. The transmission again shifted directly into 2nd gear, and the accelerator pedal became completely unresponsive. I was forced to make an emergency stop on the shoulder of the freeway with hazard lights activated due to the risk of being rear-ended by high-speed traffic and trucks. A third incident occurred on May 13, 2026, while accelerating onto Highway 99 in Modesto, California. During a shift from 4th to 5th gear, the transmission jerked violently and the vehicle suddenly lost power while merging into highway traffic. The vehicle has been taken to Mercedes-Benz of Stockton multiple times for diagnosis and repair attempts. The dealership has performed software updates and extensive testing, and dealership personnel have personally verified the transmission defect during road testing. Mercedes-Benz engineering has also become involved in the diagnosis process. However, the defect remains unresolved. This defect creates a serious highway safety hazard due to sudden loss of propulsion, uncontrolled deceleration, and loss of accelerator response while driving at freeway speeds.

NHTSA complaint #11740380 — an unverified report by a vehicle owner.

SERVICE BRAKES

3/31/26 2pm After highway driving - 3 miles/35 mph tried to brake- Immediately something was wrong with the brake as and it felt spongy/mushy/unresponsive. Car did not slow until I pressed the brake fully to the floor. The car did stop &was alarmingly unresponsive. Around this time,noticed the white BRAKE light illuminated. Continued to drive - terrified. Had to brake VERY HARD to get car to slow/stop. at home, Quick google search had me try turning on and off parking brake - tied this 5-6 times and white BRAKE light went off and I could brake/stop car. Bought car to Mercedes for service for 4:20 appointment - expressing incredibly strong reservations to Will Bane -and fear about driving car. He assured me as it is braking it should be fine. 04/01/2026 -notified car was ready for pick up/text stated: "Service is complete, everything looked good on the inspection report. No codes in the system for the brake concern and the brakes are currently working as designed" at pickup - and prior in text to will bane - i expressed significant concern about future braking issues. was told it was a "software issue and they updated it" and given a card for roadside assistance There was a recall campaign (2026010002/25p5496612) and codes were cleared as part of this unrelated recall. Brake fluid exchange was performed PRIOR to brake diagnosis Bottom line - I have significant concerns about braking.

NHTSA complaint #11730496 — an unverified report by a vehicle owner.

POWER TRAIN

•Incident Details: •Both sudden shutdown incidents •“12V Battery” warning (first incident) •“Stop - Switch Off Vehicle” warning (second incident) •That it happened with children in the car on a tollway Safety Concerns: •Loss of power steering/braking •Risk of collision •Repeated failures on a 1-year-old vehicle

NHTSA complaint #11677934 — an unverified report by a vehicle owner.

VEHICLE SPEED CONTROL

•Incident Details: •Both sudden shutdown incidents •“12V Battery” warning (first incident) •“Stop - Switch Off Vehicle” warning (second incident) •That it happened with children in the car on a tollway Safety Concerns: •Loss of power steering/braking •Risk of collision •Repeated failures on a 1-year-old vehicle

NHTSA complaint #11677934 — an unverified report by a vehicle owner.

ENGINE

•Incident Details: •Both sudden shutdown incidents •“12V Battery” warning (first incident) •“Stop - Switch Off Vehicle” warning (second incident) •That it happened with children in the car on a tollway Safety Concerns: •Loss of power steering/braking •Risk of collision •Repeated failures on a 1-year-old vehicle

NHTSA complaint #11677934 — an unverified report by a vehicle owner.

POWER TRAIN

I am writing to report a critical safety issue with my 2024 Mercedes-Benz GLC300, VIN: [XXX] , which I purchased on [XXX], from Mercedes-Benz of Walnut Creek, CA, with 9,500 miles. On [XXX], while driving on [XXX], the vehicle suddenly lost power, the transmission downshifted to 2nd gear, and the accelerator became unresponsive. I was forced to drive at 20 mph for 20 minutes on a busy freeway, posing a severe risk of a rear-end collision. I managed to exit the freeway, but this incident could have resulted in a serious accident. This failure may be related to prior recalls of the 2024 GLC300, including issues with a defective 80-amp fuse (February 2024) and a loose 48-volt battery ground connection (March 2024), both of which can cause power loss. I urge the NHTSA to investigate this incident to determine if it warrants an expanded recall or further action to protect other drivers. I have notified Mercedes-Benz of Walnut Creek CA and Mercedes-Benz USA, demanding an investigation and a refund under the California Lemon Law. Please confirm receipt of this complaint and provide an update on any investigation. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11647082 — an unverified report by a vehicle owner.

UNKNOWN OR OTHER

Attention Assist System Suspended notification comes on randomly on vehicle while driving, rendering driver defenseless with regard to safety warnings that would otherwise be in effect, such as blind spot assist, attention assist, which are vital components for safe driving. This has happened on numerous occasions, most recently on 12/06/2024 while driving under destination route guidance. It has also happened when car was stopped to retrieve mail at residence mail box and, at other times for no apparent reason, while driving. Each time when engine was restarted the dashboard read 'System suspended' and continued to do so until car was returned to dealer. This vehicle was purchased on 12/21/2023 and with less than 350 miles began repeated problems with warnings, the first of which was "Check engine"on 02/02/2024, as car was running rough. Car was repaired(dealer determined cause was electrical/software error, fault code) yet before driving out of the dealership the same 'check engine' warning reappeared and vehicle had to be returned to service that same day for the same problem. Since that date in 2023, this vehicle has had numerous seemingly computer related issues that render it unreliable as to the safety devices this vehicle features that should always be maintained. On 03/21/2024 with less than 950 miles the fans remained running after shutting vehicle off and a message appeared stating" cooling system malfunction/reduced drive performance" with a red triangle on dashboard. Dealer determined the cause was 'SOFTWARE" At this point I am concerned that this vehicle is over engineered with computerized options that randomly fail. On another occasion the lights on one side may have been on overnight. The lights (courtesy lights) were on on the right side overnight in garage. My safety is continuously at risk whenever a warning appears.I replaced my GLK specifically to have Blind Spot Assist, PRE-safe, Attention Assist, Active distance assist and other features.

NHTSA complaint #11629760 — an unverified report by a vehicle owner.

EXTERIOR LIGHTING

Attention Assist System Suspended notification comes on randomly on vehicle while driving, rendering driver defenseless with regard to safety warnings that would otherwise be in effect, such as blind spot assist, attention assist, which are vital components for safe driving. This has happened on numerous occasions, most recently on 12/06/2024 while driving under destination route guidance. It has also happened when car was stopped to retrieve mail at residence mail box and, at other times for no apparent reason, while driving. Each time when engine was restarted the dashboard read 'System suspended' and continued to do so until car was returned to dealer. This vehicle was purchased on 12/21/2023 and with less than 350 miles began repeated problems with warnings, the first of which was "Check engine"on 02/02/2024, as car was running rough. Car was repaired(dealer determined cause was electrical/software error, fault code) yet before driving out of the dealership the same 'check engine' warning reappeared and vehicle had to be returned to service that same day for the same problem. Since that date in 2023, this vehicle has had numerous seemingly computer related issues that render it unreliable as to the safety devices this vehicle features that should always be maintained. On 03/21/2024 with less than 950 miles the fans remained running after shutting vehicle off and a message appeared stating" cooling system malfunction/reduced drive performance" with a red triangle on dashboard. Dealer determined the cause was 'SOFTWARE" At this point I am concerned that this vehicle is over engineered with computerized options that randomly fail. On another occasion the lights on one side may have been on overnight. The lights (courtesy lights) were on on the right side overnight in garage. My safety is continuously at risk whenever a warning appears.I replaced my GLK specifically to have Blind Spot Assist, PRE-safe, Attention Assist, Active distance assist and other features.

NHTSA complaint #11629760 — an unverified report by a vehicle owner.

ENGINE

Attention Assist System Suspended notification comes on randomly on vehicle while driving, rendering driver defenseless with regard to safety warnings that would otherwise be in effect, such as blind spot assist, attention assist, which are vital components for safe driving. This has happened on numerous occasions, most recently on 12/06/2024 while driving under destination route guidance. It has also happened when car was stopped to retrieve mail at residence mail box and, at other times for no apparent reason, while driving. Each time when engine was restarted the dashboard read 'System suspended' and continued to do so until car was returned to dealer. This vehicle was purchased on 12/21/2023 and with less than 350 miles began repeated problems with warnings, the first of which was "Check engine"on 02/02/2024, as car was running rough. Car was repaired(dealer determined cause was electrical/software error, fault code) yet before driving out of the dealership the same 'check engine' warning reappeared and vehicle had to be returned to service that same day for the same problem. Since that date in 2023, this vehicle has had numerous seemingly computer related issues that render it unreliable as to the safety devices this vehicle features that should always be maintained. On 03/21/2024 with less than 950 miles the fans remained running after shutting vehicle off and a message appeared stating" cooling system malfunction/reduced drive performance" with a red triangle on dashboard. Dealer determined the cause was 'SOFTWARE" At this point I am concerned that this vehicle is over engineered with computerized options that randomly fail. On another occasion the lights on one side may have been on overnight. The lights (courtesy lights) were on on the right side overnight in garage. My safety is continuously at risk whenever a warning appears.I replaced my GLK specifically to have Blind Spot Assist, PRE-safe, Attention Assist, Active distance assist and other features.

NHTSA complaint #11629760 — an unverified report by a vehicle owner.

POWER TRAIN

When stopped at a light or stop sign, Vehicle will Jerk forward as If hit from behind. Very surprising and dangerous. Very intermittent. The has happened many times. Vehicle will at times have rough downshifts. Ie. overdrive (9th) to (8th) gear. also intermittent. This has happened multiple times. Vehicle was taken to the dealer twice for a total of 50 hours in the shop. The first service time no problem was found, diagnostics did not show problem. Aug 22 to Aug 30, 2024. The second service time Oct 3 to Nov 14, 2024. Problem was duplicated by the technician. Vehicle diagnostics still did not show a problem. Technician replaced the transmission valve body, did various software checks at the request of the factory. The engine control unit was then changed based on data supplied to the factory. At this point technician checked the car and dealers believes car is fixed. Vehicle has been returned to us on Nov 14 2024. We have requested the vehicle be bought back or replaced.

NHTSA complaint #11625278 — an unverified report by a vehicle owner.

ELECTRICAL SYSTEM

When stopped at a light or stop sign, Vehicle will Jerk forward as If hit from behind. Very surprising and dangerous. Very intermittent. The has happened many times. Vehicle will at times have rough downshifts. Ie. overdrive (9th) to (8th) gear. also intermittent. This has happened multiple times. Vehicle was taken to the dealer twice for a total of 50 hours in the shop. The first service time no problem was found, diagnostics did not show problem. Aug 22 to Aug 30, 2024. The second service time Oct 3 to Nov 14, 2024. Problem was duplicated by the technician. Vehicle diagnostics still did not show a problem. Technician replaced the transmission valve body, did various software checks at the request of the factory. The engine control unit was then changed based on data supplied to the factory. At this point technician checked the car and dealers believes car is fixed. Vehicle has been returned to us on Nov 14 2024. We have requested the vehicle be bought back or replaced.

NHTSA complaint #11625278 — an unverified report by a vehicle owner.

ENGINE

When stopped at a light or stop sign, Vehicle will Jerk forward as If hit from behind. Very surprising and dangerous. Very intermittent. The has happened many times. Vehicle will at times have rough downshifts. Ie. overdrive (9th) to (8th) gear. also intermittent. This has happened multiple times. Vehicle was taken to the dealer twice for a total of 50 hours in the shop. The first service time no problem was found, diagnostics did not show problem. Aug 22 to Aug 30, 2024. The second service time Oct 3 to Nov 14, 2024. Problem was duplicated by the technician. Vehicle diagnostics still did not show a problem. Technician replaced the transmission valve body, did various software checks at the request of the factory. The engine control unit was then changed based on data supplied to the factory. At this point technician checked the car and dealers believes car is fixed. Vehicle has been returned to us on Nov 14 2024. We have requested the vehicle be bought back or replaced.

NHTSA complaint #11625278 — an unverified report by a vehicle owner.

FORWARD COLLISION AVOIDANCE: AUTOMATIC EMERGENCY BRAKING

The reverse sensors are faulty, causing the GLC300 model to randomly auto-brake while going in reverse. My driveway is flat and long with no significant grade changes and this has occurred at another location as well with similar topography. There are no obstructions present nor any significant grade changes, the vehicle auto-brakes not everytime, happens out of the blue once every 8-12 tries. My new vehicle has been checked out by Mercedes-Benz of Cary service department 2 times, since buying new April 2024. They brought my car out to my house themselves and experienced the auto-braking first hand. They brought out a second GLC300 and it auto-braked as well. The technicians have calibrated, and updated the sensors to no avail. My driveway is long and flat with a slight slope at the end, but it happened to me at my friends house who's driveway is all flat. This is a serious safety risk for me and all passengers. It makes everyone tense not knowing next time it may happen. No matter the revering speed, or if you keep your foot on brake lightly as you are backing up, the glc300 randomly will auto-brake without any warning lights or sounds. The tires screech, it locks up in an instant. It is frightening and we are scared to anticipate the next occurrence or risk bruising our body or head injury. Even when I manually over-ride the rear and/or surrounding sensors, turning them off temporarily as I back up in reverse- the car will still auto-brake. Mercedes has yet to agree with me that this is a safety issue and on 11/8 asked me to pick up the car. I refused until the issue is fixed. They still have my car in service, it has been 3 weeks since 10/18/24. This was the 2nd time I brought in in for this issue since I bought new March 30 2024. I called corporate to ask them to buy back the car if the issue cannot be fixed, they have yet to respond.

NHTSA complaint #11624989 — an unverified report by a vehicle owner.

SEAT BELTS

Passenger backseat seatbelt would not release under any circumstance. I tried turning the car off and on again. Checking settings on the screen and even releasing the seat a bit. Pushing the red button on the buckle did nothing. Pulling did nothing. Eventually had to cut the seatbelt to get the passenger out. And it is still stuck in the buckle.

NHTSA complaint #11613147 — an unverified report by a vehicle owner.

UNKNOWN OR OTHER

OUR SUV IS 6 WEEKS NEW AND WAS PURCHASED NEW AT THE MERCEDES DEALERSHIP. REAR HATCH: WHEN STANDING BEHIND VEHICLE REAR DOOR HATCH CLOSES RANDOMLY WITH NO WARNING OR BEEP. CLOSES VERY QUICKLY AND HITS HEAD VERY HARD. FEET ARE NOT NEAR THE BUMBER WHICH ELIMINATES THE REAR FOOT ACTION THAT CLOSES THE HATCH. WHEN THE HATCH HITS YOUR HEAD IT COULD KNOCK YOU OUT ESPECIALLY IF YOUR EDERLY OR A CHILD. ALSO IF YOU TRY AND STOP THE HATCH COSING ITS VERY STRONG AND TAKES A LOT OF STRENGTH. WHEN YOU USE THE REMOTE OR BUTTON IN CAR TO OPEN HATCH IT OPENS SO FAST AND BEEPS TO LATE TO ALERT DOOR IS OPENING. VERY DANGEROUS. THIS PROBLEM HAPPEN SEVERAL TIMES AND IS RANDOM. THE LAST TIME IT HAPPEN WAS SUNDAY 9-1-24 WHILE LOADING GROCERIES AT COSTCO

NHTSA complaint #11612085 — an unverified report by a vehicle owner.

VISIBILITY/WIPER

I purchased the car brand new from my local dealership and 3 months after purchase my windshield cracked. I had the entire windshield replaced with an OEM windshield on 5/7/2024 and yesterday I got another chip/crack in my windshield. I have only had my car less than 8 months and already had 2 cracks/chips. I owned my previous Mercedes over 6years and never had an chip or crack. This has to be a defect in the windshield. My friend also just purchased a 2024 GLC 300 and it's only 3 months old and her windshield is also cracked. I look forward to hearing from you.

NHTSA complaint #11597905 — an unverified report by a vehicle owner.

ELECTRICAL SYSTEM

The contact owns a 2024 Mercedes-Benz GLC300. The contact stated that while driving at an undisclosed speed, the audible alarm activated and several warning lights illuminated. The contact stated that all the warning lights went off except the check engine and the low-battery warning lights. The vehicle was taken to the dealer. The vehicle had not been diagnosed or repaired. The contact stated that the vehicle was previously taken to the dealer on three occasions because of electrical or software failure. The manufacturer was made aware of the failure and a case was filed. The failure mileage was approximately 2,174.

NHTSA complaint #11578547 — an unverified report by a vehicle owner.

ELECTRICAL SYSTEM

Check engine light appears, also a blue engine and a turtle. The dealer is aware, they have had it 3times for the same issue and this time 23 days and counting. Currently Mercedes has no fix. I purchased the veh 30 Nov 23- first appeared 16 dec and continued going on and off.

NHTSA complaint #11574918 — an unverified report by a vehicle owner.

ENGINE

Check engine light appears, also a blue engine and a turtle. The dealer is aware, they have had it 3times for the same issue and this time 23 days and counting. Currently Mercedes has no fix. I purchased the veh 30 Nov 23- first appeared 16 dec and continued going on and off.

NHTSA complaint #11574918 — an unverified report by a vehicle owner.

EXTERIOR LIGHTING

When driving the car at night with the headlights on, you notice a dark, thin object illuminated from the left front headlight approximately 50-75 feet ahead of the vehicle that will move as the steering is turned, either left or right. It looks like a thin pedestrian moving into the path of the car. I noticed this defect within the first few weeks of ownership. I took the car to the dealership and showed my pictures of the lights with the shadow at night to two Mercedes Benz of Sarasota employees. The dealership ran multiple diagnostic tests and determined the car was operating as designed. While the dealership had my car, two employees at the dealership noted they had relatives who had 2024 Mercedes Benz vehicles and had noticed this same issue. They also received the same explanation that this was the design of the headlights. It is concerning, as it could cause a driver to swerve or otherwise create an issue that leads to an accident. I request NHTSA look into this headlight issue and encourage Mercedes Benz to fix this before an accident happens. I have uploaded the work order documents from the dealership. I have uploaded a picture of the shadow reflected on a car ahead of me to show the shadow up close.

NHTSA complaint #11574540 — an unverified report by a vehicle owner.

ELECTRICAL SYSTEM:12V/24V/48V BATTERY

The contact owns a 2024 Mercedes-Benz GLC300. The contact stated that upon starting the vehicle, the check engine warning light illuminated. The vehicle was taken to a dealer and the contact was informed that the 48V bolt battery had caused the check engine warning light to illuminate. The contact was informed by the dealer that the temporary fix would be to reduce the battery charge to 25% then charge the battery to 75%. The check engine warning light returned soon after the fix and the contact was informed that there was no permanent fix for the defect. The manufacturer had yet to be notified of the failure. The vehicle had yet to be repaired. The failure mileage was approximately 1,800.

NHTSA complaint #11566466 — an unverified report by a vehicle owner.