2020 Mercedes-Benz C300: check engine light

Filed Apr 23, 2026 · Electrical, Engine · NY

Vehicle has ongoing and recurring electrical and engine-related defects that affect safe operation. The primary systems involved are the electrical system, engine ignition system, and powertrain. The vehicle is available for inspection upon request. Prior service records show issues beginning in 2020 involving repeated electronic system failures requiring multiple repairs and component replacements. Since purchasing the vehicle in April 2023, the vehicle has developed more serious failures, including: – September 2024: Check engine light with loss of power and inability to exceed safe driving speeds – October 2024: Engine misfiring due to ignition coil failure requiring replacement of ignition components – September 2025: Additional ignition coil electrical fault (code P0353) The problem has been reproduced and confirmed through dealership service inspections and diagnostic reports. Warning indicators, including the check engine light, appeared prior to failure events. These defects create a safety risk due to potential loss of power, engine failure, and unreliable vehicle operation while driving, which could increase the risk of an accident. The issues have required multiple repairs without permanent resolution and appear to be ongoing and worsening over time.

Filed Feb 17, 2026 · Engine · GA

I am reporting a catastrophic repeat engine failure on my 2020 Mercedes-Benz C300. On October 9, 2025, with 26,589 miles, the vehicle suffered a Cylinder 2 failure (exhaust valves), causing a dangerous loss of power in traffic. I paid $4,100.43 for a $10,000 plus cylinder head replacement at an authorized dealer (Mercedes-Benz of Atlanta South) on November 13, 2025. Following the repair, the vehicle continued to exhibit multiple 'Check Engine Oil Level' warnings. On February 4, 2026—less than 90 days after the major repair—the engine suffered a total catastrophic failure. The dealer now states the entire engine requires replacement. This repeat failure of a critical engine component at low mileage poses an unreasonable risk of stalling or sudden loss of propulsion on high-speed roads. I am aware of the January 2026 Mercedes-Benz warranty extension (NCU 30-P-072328) for this specific M264 engine defect, which confirms a known manufacturing flaw that the current dealership repair process failed to remediate, leaving me in an unsafe vehicle.

Filed Oct 26, 2025 · Engine, Fuel system · GA

I purchased this 2020 Mercedes-Benz C300 only two months ago and have driven it less than 3,000 miles. The Carfax report shows consistent maintenance and regular service history by prior owners. While driving, the check engine light came on and the vehicle began shaking and running roughly. Diagnostics by Peachtree Imports (10/03/2025) and later by Mercedes-Benz of Atlanta South confirmed Cylinder #2 failure on the M264 2.0L engine at only 26,589 miles. The dealer’s report states: “Cylinder #2 mixture formation out of spec. Fault occurred due to worn exhaust valve seat. Cylinder head replacement required.” Estimated repair cost: $10,470.66. This causes misfire, loss of power, and unsafe drivability. The failure matches Mercedes-Benz Technical Service Bulletin LI01.30-P-072328 (2021), which documents valve-seat leakage in M264 engines requiring head replacement. The vehicle is outside warranty but has extremely low mileage, and MBUSA Case #18392667 remains unresolved. It is also important to note that the M260 engine, which is mechanically identical to the M264 but mounted transversely, has already received a warranty extension from Mercedes-Benz for the same cylinder-head and valve-seat defect. This indicates a systemic issue across both engine families, presenting a safety risk of sudden power loss or engine stall during operation.

Filed Apr 11, 2025 · Engine · WA

I own a 2020 Mercedes-Benz C300, and the check engine light recently came on. The vehicle has only around 27,000 miles and has been regularly maintained at an authorized dealership. Diagnostic testing revealed fault code P06DA00, indicating an electrical failure or open circuit in the engine oil pump control valve. The dealership confirmed that the valve could not actuate and provided a repair estimate exceeding $7,000 due to the labor-intensive nature of the repair. This issue occurred shortly after the factory warranty expired. The sudden loss of power while driving could pose serious safety risks under different traffic conditions. I believe this may be a manufacturing defect that could potentially affect other vehicles of the same model. This issue occurred shortly after the factory warranty expired. The way the vehicle lost power suddenly while driving could have posed serious safety risks in different traffic conditions. I believe this could be a manufacturing defect and may affect other vehicles of the same model.

Filed May 17, 2024 · Engine, Transmission · VA

My wife was driving our 2020 Mercedes Benz C300 coupe near our house and the engine light came on. Then the car could not be driven over the speed of 30 miles per hour. Then it stopped and had to be towed. Fortunately, she was able to avoid being hit by other vehicles.The car only has 25219 miles. It was towed to a mechanic who performed a diagnostic test which provided a series of codes regarding the malfunction. Three codes were related to the CAMTRONIC camshaft system and its Solenoid ( Codes: P003C-53; P34AE-00; P34AD-09). Camshaft position actuators Failure codes: P34AD; P34AE. The way it happened could have resulted in damage, serious injury or death since the car suddenly stopped. The car is well maintained. We believe that there is a manufacturer's defect since this is a garaged vehicle that is well maintained and has low mileage.

Filed Oct 25, 2022 · Driver assistance, Fuel system · NC

The component that failed was the fuel injector and spark plug. A few months prior to this incident, I was making a left hand turn, when the accelerator completely gave out. I was making the left on a blinking yellow arrow, luckily the on coming car was not coming at me fast or I would've been in an accident due to the accelerator failing. I had to pull over, turn the car off and then back on to reset it. I was told by the dealership service center that they could not find anything and that there have been no complaints or recalls. After about 8 months of owning the vehicle, it started to have problems turning over when the engine on/off button was pressed. I was repeatedly told that they could not do anything if it did not happen in the dealership service center. This past week on 10/20/2022, while I was driving down the freeway, when I went to accelerate and at that moment the vehicle began to stutter/shake uncontrollably. After that, any time the accelerator was pressed it would shutter/shake. My vehicle was towed to a dealership. Come to find out, cylinder one was coding. They found out that the fuel injector was stuck open. According to the service advisor, that issue was causing a misfire. I was told that they replaced the fuel injector and the spark plug. According to the vehicle report I was given, 1 reman injector, 4 TS spring F In, 1 spark plug, and there was a core return (not sure what that means). The check engine light came on right away. In addition to the incidents above, I have had the forward collision alert come on when nothing is in front of me. I worry that one day it will cause my vehicle to engage the brakes when nothing is around.