32 of the
609 complaints filed about the Mercedes Benz GLC 300
are about the transmission —
5% of everything owners reported.
The worst model year for it is 2018.
32
Complaints
5%
Share of all complaints
1
Crashes
0
Fires
Transmission & Drivetrain complaints by model year
My 2020 Mercedes-Benz GLC 300 triggered check engine light with code P06DA (engine oil pressure control) at 40,000 miles. The failed component is an oil pressure control sensor/solenoid worth approximately $200. However, due to Mercedes-Benz's engine design (M264 engine), the entire engine must be removed from the vehicle to access and replace this part. Repair estimate from authorized Mercedes-Benz dealership (Mercedes-Benz of Stevens Creek): $8,391. SAFETY CONCERN: Loss of oil pressure can cause catastrophic engine failure while driving. Engine seizure at highway speeds poses serious risk of loss of vehicle control, potential accident, and harm to occupants and other drivers. This is a known, widespread design defect affecting Mercedes-Benz vehicles equipped with M264/M274 engines across multiple model lines: GLC 300 (2019-2023) C 300 (2019-2023) E 300 (2019-2023) GLC 43 AMG, C 43 AMG GLB 250, A 220, CLA 250 Mercedes-Benz's own authorized dealership confirmed they are "seeing this issue more and more." Despite awareness of this widespread defect, Mercedes-Benz has not issued a recall or Technical Service Bulletin. The design makes repair financially prohibitive ($8,000+), meaning many owners continue driving with compromised oil pressure — creating an ongoing safety hazard on public roads. Mercedes-Benz refused to repair under goodwill, then denied repurchase after 30-day review. They have left consumers with no remedy for a known safety-related design defect. I am requesting NHTSA investigate this as a safety defect affecting potentially hundreds of thousands of vehicles.
NHTSA complaint #11746524 — an unverified report by a vehicle owner.
Component Failure: The vehicle is equipped with the M274 2.0L turbocharged engine, which suffered a major internal mechanical defect. An authorized Mercedes-Benz dealership diagnosed the vehicle at 79,504 miles with a malfunction in the crankcase ventilation system alongside severe internal defects, quoting a total repair estimate of $9,851 to perform extensive engine work. Safety Risk: This known manufacturing defect involves premature failure and cracking of the pistons, which poses an immediate safety hazard due to potential catastrophic engine failure and sudden, complete loss of motor power while driving at highway speeds. The manufacturer has failed to offer an extended warranty or recall for this known issue on the 2018 model year.
NHTSA complaint #11741952 — an unverified report by a vehicle owner.
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.
I have had my car for almost two years. This problem has been on-going the whole time. It happens intermittently, I never know. I will be driving it and usually when I am making a turn or pulling onto a main road, you press the gas to go and the car hesitates and makes a loud brooooooooom sound like it is trying to go or figure out what to do and if you are pulling out onto a main road with on comming traffic, this is dangerous. We have seen information that on the 2019 and 2018 GLC300's this has been documented, my car is a 2020 but it's the same thing. It's like the car hesitates and slows down when it should go!
NHTSA complaint #11737705 — an unverified report by a vehicle owner.
On April 16, 2026, within minutes of being released from a certified dealership, my 2019 Mercedes-Benz GLC 300 suffered a sudden and total loss of propulsion while traveling at high speed on the Belt Parkway (NY). Despite depressing the accelerator, the vehicle failed to maintain speed and stalled in active traffic. This created an immediate life-safety hazard, forcing me to navigate across multiple lanes without engine power to avoid a high-speed rear-end collision. The vehicle was released to me by Mercedes-Benz of Brooklyn on April 16, 2026, following a repair for which I paid $2,134.94. The dealership diagnosed the issue as a wiring harness/sensor fault and formally certified the vehicle as "Found OK" and safe for operation. The catastrophic failure occurred only 22 minutes after I departed the dealership lot. The vehicle had to be towed back to the facility immediately. Upon the vehicle being towed back on April 16, the dealership admitted via recorded voicemail that the initial $2,134.94 repair was a misdiagnosis. They subsequently issued a new diagnosis for a "Valve Body" failure and a new quote of $6,424. The dealership's Service Director has since admitted the vehicle suffers from concurrent transmission and engine failures, rendering the car a liability. This represents a critical failure of the powertrain and electronic control systems. Releasing a vehicle that suffers a total power loss on a highway immediately after a "certified" repair is gross negligence. I am reporting this to NHTSA as a catastrophic failure of a safety-critical component (Transmission/Valve Body) that resulted in a "dead-stick" situation on a major New York thoroughfare, posing a severe risk to myself and other motorists. The vehicle remains at the dealership. Mercedes-Benz USA has offered only a $2,000 "goodwill credit," which does not address the safety defects or the initial misdiagnosis. No recall has been initiated for this batch.
NHTSA complaint #11736351 — an unverified report by a vehicle owner.
The engine starts shaking, smell of gas car than stops while driving, could caused an accident and severely injured someone on the freeway. This is a major safety issue after further researching this particular issue MB of Canada issue a warranty letter extension for this particular but nothing for US.
NHTSA complaint #11724468 — an unverified report by a vehicle owner.
Vehicle Information: Year: 2021 Make: Mercedes-Benz Model: GLC 300 Engine: M264 Mileage at time of failure: Approximately 65,000 miles Complaint Description: While driving, my 2021 Mercedes-Benz GLC 300 began experiencing repeated engine misfires and rough running, accompanied by a persistent check engine light. These symptoms began shortly after I purchased the vehicle and progressively worsened over time. The vehicle exhibited reduced engine performance and hesitation while driving. The condition was intermittent at first but became more frequent, indicating a progressive mechanical issue rather than a sudden failure. At approximately 65,000 miles, the vehicle was evaluated by an authorized Mercedes-Benz dealership and diagnosed with a catastrophic cylinder head failure, requiring full cylinder head replacement. The estimated repair cost is approximately $8,000. The vehicle has never been modified and has not undergone prior engine repairs. The failure occurred well before what would be considered normal wear for an engine component of this type. Based on the progression of symptoms, the dealer diagnosis, and similar reports from other owners of the same model and engine, this appears to be a systemic defect involving the cylinder head and valve train, rather than an isolated incident or maintenance-related issue. This condition presents a potential safety concern due to loss of engine performance, drivability issues, and the risk of reduced power while operating the vehicle.
NHTSA complaint #11709709 — an unverified report by a vehicle owner.
The contact's friend owns a 2018 Mercedes-Benz GLC 300. The contact stated that while the owner was driving at an undisclosed speed, the accelerator pedal was depressed, but the vehicle failed to accelerate as intended, and the gear shifter independently shifted to neutral(N). No warning lights were illuminated. In addition, the contact stated that the failure was persistent. The contact stated that the owner forced the gear shifter out of neutral(N). The vehicle was taken to the dealer, where it was diagnosed that the transmission control unit had failed and needed to be replaced. The vehicle was not repaired. The contact related the failure to an unknown recall, but the VIN was not included in a recall. The manufacturer was made aware of the failure, and a case was filed. The contact was advised to contact the NHTSA Hotline to report the failure. The failure mileage was unknown.
NHTSA complaint #11708077 — an unverified report by a vehicle owner.
The contact owns a 2018 Mercedes-Benz GLC300. The contact stated that while driving at various speeds, the vehicle shifted into gear initially without warning. The contact stated that while stopped at a light, the vehicle shut off with the "Transmission Malfunction Stop" message displayed on the instrument panel. The contact was unable to move the vehicle, and the vehicle was towed to an independent mechanic. The mechanic ran a diagnostic test on the vehicle and initially stated that the front drive wheel sensor was defective; however, the contact was then informed that there were no issues with the sensor. Neither the dealer nor the manufacturer was notified of the failure. The vehicle was not repaired. The failure mileage was approximately 90,000.
NHTSA complaint #11702561 — an unverified report by a vehicle owner.
The contact owns a 2019 Mercedes-Benz GLC300. The contact stated that while shifting from reverse to drive, the vehicle stalled and remained in neutral. After the vehicle stalled, the vehicle took approximately 8 minutes before the vehicle could be shifted into drive. Once in drive, the vehicle would jerk and shift to D3 before accelerating. The check engine warning light would illuminate while in reverse. The vehicle was taken to the dealer, who diagnosed a transmission failure due to a malfunctioning valve body and low pump pressure. The dealer confirmed that the VIN was not under recall and that the issue was not covered under warranty. The vehicle was not repaired. The contact informed the manufacturer of the failure, and a case was opened. The manufacturer referred the contact to the NHTSA Hotline to report the failure. The failure mileage was approximately 60,000.
NHTSA complaint #11700738 — an unverified report by a vehicle owner.
The contact owns a 2022 Mercedes-Benz GLC300. The contact stated that while driving 60 MPH, the accelerator pedal was depressed; however, the vehicle failed to accelerate as intended. The contact stated that there were several unknown warning lights illuminated before the engine seized. The vehicle was restarted; however, while driving at an undisclosed speed, the failure reoccurred. The contact started the vehicle again, and the vehicle was slowly driven to the residence. The vehicle was not diagnosed or repaired by an independent mechanic or the dealer. The manufacturer was not made aware of the failure. The failure mileage was approximately 51,519.
NHTSA complaint #11682886 — an unverified report by a vehicle owner.
The contact owns a 2019 Mercedes-Benz GLC300. The contact stated that while stopped at a stoplight on a hill, the vehicle rolled backwards. The contact stated that the brake pedal was depressed to stop the vehicle from rolling backwards, preventing the vehicle from hitting the vehicle behind. The contact stated that the failure had occurred several times. The vehicle was taken to the dealer; however, the failure was not duplicated. The contact was informed that rolling backwards was normal. The manufacturer was not made aware of the failure. The failure mileage was approximately 63,500.
NHTSA complaint #11680717 — an unverified report by a vehicle owner.
Defect Summary: Since 2024, my 2022 Mercedes-Benz GLC300 has had a persistent, abnormal engine noise consistent with the sound of a 4-cylinder diesel engine, despite being gasoline-powered. The noise occurs both while idling and in motion. On several occasions, the coolant warning light illuminated while the noise persisted. The defect has worsened over time, becoming louder and more frequent. Events & Safety Risks: The dealership repeatedly claimed “no problem found” because no warning lights appeared and no scanner codes were present, ignoring my time-stamped video evidence. At one point, I was advised to drive the vehicle from Morgan Hill, CA to the dealership while making the loud noise for diagnostics — an unsafe recommendation. When the coolant warning light appeared, the service department planned only to top off coolant. I insisted on a diagnostic, which revealed a coolant hose leak. Driving with a leak could cause overheating and sudden engine failure, creating a serious safety hazard for myself, my child, and other motorists. Repair History: Multiple visits to Mercedes-Benz of San Jose (2024–2025) for the same defect. Each time, the defect was dismissed or not resolved. No meaningful repairs were performed. The issue persists today. Evidence: Time-stamped video proof of defect, full service records, and documentation of correspondence with the dealership are available. Safety Concern: This unresolved defect creates a risk of sudden engine failure or overheating while driving, potentially causing loss of control or stranding occupants in unsafe conditions.
NHTSA complaint #11678034 — an unverified report by a vehicle owner.
•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.
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.
The component that failed was the right front differential. My safety and the safety of others was put at high risk as I was driving at 60 mph on the highway and my vehicle suddenly and abruptly reduced speed to about 15mph without any warning. This created an extremely dangerous and potentially hazardous situation as I tried to maneuver my car at this very low speed on the highway in the middle lane safely to the side of the highway. Cars around me quickly maneuvered around me in attempts to avoid my slow moving vehicle and not hit me. The entire experience was terrifying, especially given that the car gave no prior indication of a malfunction. The vehicle had to be towed to Mercedes. I have no real answers from Mercedes as to the cause or why the vehicle did not notify me or why the service light did not go on. The vehicle only had 51,000 miles and is well taken care of. Because the car was out of warranty they refused to cover the expense. I called and sent letters to corporate and received $2500 towards a $6000 bill. I feel this was a safety issue and my car shut down without any type of warning and Mercedes should cover all repair costs. The car has been repaired, but I am still nervous to drive it.
NHTSA complaint #11641513 — an unverified report by a vehicle owner.
Vehicle experienced transmission shifting issue after having driven for a period of 15 - 20 minutes, with engine oil temp reaching above 103/105 degrees C, transmission won't shift into Drive. Automatically pops into Neutral. Other times engine will stall, required complete restart. This creates hazard for operator and cars following behind as driver needed to steer vehicle out of the way of traffic while in Neutral. Independent MB repair shop and dealership scanned vehicle and identified with code P073E code. Dealer upgraded TCM control module software, and wanted to replace valve body in hope of remedy the problem. They were not 100% certain problem will be fixed. Independent repair shop indicated MB need to issue a recall for this problem, as they have seen many owner faced with the same problem. This is a big safety issue with problem of the transmission control module. Problem can be reproduced.
NHTSA complaint #11632530 — an unverified report by a vehicle owner.
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.
Transmissiongoes into neutral while driving car at times. sometimes it will not go back into gear No movement of car on freeway potential of being hit from behind. problem reproduced, inspected by independent shop not inspected no lights
NHTSA complaint #11621613 — an unverified report by a vehicle owner.