*Median odometer reading when the problem happened, where owners gave one. One complaint can name several problem areas.
Electrical system
On October 23, 2026, my 2020 Mercedes-Benz GLC 300 unexpectedly lost engine power while I was in traffic, without advance warning. When I attempted to restart it, the engine started, shook, and shut off again. A 12-volt battery warning appeared during the incident. On October 26, a dealership representative told me a software issue caused the shutdown and that a software update was needed. They said the update would be performed at no charge, although I would owe a diagnostic fee. I am concerned that the vehicle could lose power without warning again, especially at highway speeds. I am requesting that NHTSA review this incident for a possible safety defect.
Oct 23, 2026Engine
My check-engine light recently illuminated, and diagnostic testing identified fault code P06DA00, relating to the oil pump control valve circuit. I have been quoted over $5,000 to replace the oil control valve and oil pump harness. I was quoted the following by Mercedes Servuce in Manchester, NH- Oil Pressure Regulator Valve: need to remove lower oil pan only to access oil control valve and replace the valve and sub harness. $5013.52. This is a known issue. My vehicle has been well maintained, and I have been advised that it is otherwise in excellent mechanical condition. I intend to keep and drive this vehicle for many more years, which makes it particularly disappointing to encounter a…
Jul 28, 2026Forward collision avoidance › Automatic emergency braking
What component or system failed or malfunctioned, and is it available for inspection upon request? The Forward Collision Avoidance / Active Brake Assist (Automatic Emergency Braking) system failed by falsely identifying a non-existent threat and initiating uncommanded emergency stopping. The vehicle and its onboard control modules are fully available for physical and diagnostic inspection upon request. How was your safety or the safety of others put at risk? While traveling at approximately 35 mph, the vehicle suddenly executed maximum emergency braking with zero warning and no preceding obstacles, vehicles, pedestrians, or road hazards present. The violent deceleration caused maximum…
Aug 28, 2026Engine
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…
May 4, 2026Engine
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!
Jun 23, 2024Exterior lighting
There was a recall on headlight leaking and this happened to my left headlight no damage but leaking and this caused headlight to not work
Feb 10, 2026Visibility › Sun/moon roof assembly
The contact owns a 2020 Mercedes-Benz GLC300. The contact stated that while driving at an undisclosed speed, the panoramic roof unexpectedly shattered. There was no warning light illuminated. The vehicle was taken to the dealer, where it was determined that the panoramic sunroof and the sunroof protector needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure, and a case was opened. The approximate failure mileage was 53,035.
Feb 3, 2026 · 53,035 milesEngine
Premature oil pump failure on a 2020 Mercedes-Benz GLC 300 with 71,000 miles. The check engine light illuminated on December 29th, 2025 and with no other warning symptoms. The vehicle has been maintained properly, including regular visits to Mercedes-Benz dealerships. The oil pump is a critical engine component that should not fail at this mileage. It has been recommended to not drive the vehicle without repairing as oil can leak onto a hot engine. This issue has been confirmed by a Mercedes dealer. Mercedes-Benz has offered $1,000 in goodwill on a $7,400 repair, which is unreasonably low given the nature of the failure. The dealer is advocating for higher goodwill, but corporate has…
Dec 29, 2025
Owner complaints are submitted to NHTSA by the public and are not verified. Shown as filed (NHTSA removes personal details); long reports are shortened.