2021 Mercedes-Benz GLC 300 engine problems

Filed Aug 30, 2026 · Engine, Fuel system · CA

The vehicle is experiencing an intermittent, sudden, and life-threatening drop into "limp home mode" while driving, creating an severe speed differential with surrounding traffic.First Incident (50,584 miles): The vehicle entered limp mode. Authorized Mercedes service center scanned the car, confirming Fault Code P019185 (Rail pressure sensor malfunction / signal above permissible limit value). The dealer applied an Engine Control Module software patch under Mercedes TSB LI07.70-P-078047.Second Incident (53,695 miles): Less than 3,000 miles later, the exact same sudden powertrain failure recurred. The vehicle drastically lost propulsion power immediately after exiting a high-speed freeway, leaving the driver in an incredibly vulnerable, unsafe position.The manufacturer's documented software remedy has completely failed to fix the underlying powertrain defect, leaving a known hardware component failure unaddressed while actively endangering vehicle occupants.

Filed May 20, 2026 · Engine · AL

While driving in my neighborhood at 25 MPH, my Mercedes GLC300 suddenly lost power and the check engine light illuminated. My car would no longer exceed 25-30 MPH, but I drove it straight to the dealership and they said it was a faulty cylinder head and will cost $10,000 to fix! After intense negotiations, they agreed to fix it for $4,205.58, which was better, but still, that’s a lot to pay for a manufacturer’s defect! My car is a 2021 with only 67,540 miles on it.

Filed May 5, 2026 · Engine · NJ

Getting P06DA trouble code meaning that there is something wrong with the oil pressure solenoid in the oil sump. this is a known issue where the wiring of the solenoid get frayed. cost of repair for the (cheap part) is $7,500 because of 18 hour labor involved. MB knows this is an issue with the wiring in the solenoid. I'm not sure if there is a fire risk because of the frayed wires.

Filed Feb 17, 2026 · Electrical, Engine · FL

This is a well-known issue with these engines. See TSB (Service Bulletin) The 2021 Mercedes-Benz GLC 300 has 42,000 miles and the warranty ran out 2 weeks ago. The vehicle is up-to-date on service. Fault code P06DA00 Engine Oil Pressure Control Circuit/Open. The Yellow Check Engine Light came on and the engine does not run properly and causes engine damage. We had to drive it slowly, under 45 mph, to the nearest dealership. This is a safety issue. To replace the oil pump control valve solenoid and the wire harness for this feature is $5009.00 at Mercedes-Benz. The part cost is about $300 retail, and the rest is all labor fees.

Filed Jan 8, 2026 · Engine, Transmission · CA

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.

Filed Jan 8, 2026 · Engine · NJ

Cylinder head valve seat leak ..vehicle Mia fires and check engine light on

Filed Dec 30, 2025 · Engine · NJ

While I was driving on the Garden State Parkway, my vehicle experienced a sudden loss of power and persistent misfires and my check engine light came on. I was put in a position of a significant crash risk due to the fact that the vehicle loss sudden acceleration power while entering the parkway. I was almost rear ended by another vehicle. I drove immediately to a Mercedes-Benz dealer. The dealer confirmed a catastrophic cylinder head engine failure. The vehicle had only 39,000 miles. After some investigating, there have been numerous complaints from vehicle owners with the same issue on the M264 engine (which is what my vehicle has). I request that the federal safety agency investigate the premature cylinder head engine failure. Not only was I put at risk for a possible significant accident, the manufacturer has refused to consider some reimbursement for my $10,000 repair. The vehicle was only 3,000 miles out of warranty at the time of the engine failure. A safety issue seems to be warranted and possibly a recall because of the many complaints on the GLC website. Please investigate.

Filed Nov 12, 2025 · Engine · VA

There is a hesitation in or "shuddering" that causes the car to go into limp mode while in operation. I was in traffic and the car just powered down and would not get up to and or maintain speed. I contacted the local dealership and was told that there are other models and or engines in this car that have this issue and that they actually have a recall on this issue. The dealership noted that they have 1 or more that require this exact repair on every single week. The dealer told me what was wrong with it by the code it threw... He didn't have any hesitation because he is so familiar with this issue. The warning lights came on after the car powered decreased... there was no "pre" warning that this was going to happen.

Filed Oct 28, 2025 · Engine · TX

Twice my car slowed down tremendously in traffic because of a bad cylinder head. I drive a 2021 Mercedes GLC 300 4matic with 33,529 miles. In reviewing other complaints, this is a common and known complaint. My check engine light came on and I could not go over 40 mph. This is very dangerous.

Filed Oct 24, 2025 · Engine · AZ

Car has experienced rough idling, sluggish to no acceleration, check engine light illuminates and no shifting of gears regardless of speed. It appears to be going into limp mode. This has occurred monthly for the last four months. After pulling over, the car is turned off, wait five seconds and then turn it back on the car operates like nothing has happened. Here is when it has happened: 1.In a drive-thru lane to get some food 2.Waiting in a left-hand turn land 3.Driving through a parking lot at 10 mph 4.Driving on a road at 45 mph The date below is the last occurrence.