2021 Mercedes-Benz C300

The 2021 Mercedes-Benz C300 is a popular luxury sedan known for its comfortable ride, stylish interior, and advanced technology. The standard engine is a 2.0L turbocharged inline-4 producing 255 horsepower and 273 lb-ft of torque, paired with a 9G-TRONIC 9-speed automatic transmission. Some owners appreciate the C300’s fuel efficiency and elegant design, while others find the infotainment system complex and the rear seat space somewhat limited. While generally reliable, some common issues have surfaced with the 2021 C300.

Engine

2.0L Turbocharged Inline-4

• Camshaft Adjuster Failure
  • Description/Symptoms: The engine may exhibit rough idling, misfires, loss of power, and potentially a check engine light with codes related to camshaft position. It may also make rattling noises, especially on startup.
  • Solution: Replacement of the camshaft adjuster/phaser.
  • Estimated Cost to Fix: $1,500 - $2,500+
• High-Pressure Fuel Pump Failure
  • Description/Symptoms: Difficulty starting, especially when cold, hesitation during acceleration, and potential stalling. A check engine light may illuminate with codes related to fuel pressure.
  • Solution: Replacement of the high-pressure fuel pump.
  • Estimated Cost to Fix: $1,000 - $2,000+
• Turbocharger Wastegate Actuator Failure
  • Description/Symptoms: Loss of boost pressure, reduced engine power, and a check engine light. The car may feel sluggish and unresponsive.
  • Solution: Replacement of the turbocharger wastegate actuator.
  • Estimated Cost to Fix: $800 - $1,500+

Transmission

9G-TRONIC 9-Speed Automatic

• Rough or Delayed Shifting
  • Description/Symptoms: Harsh or jerky shifts between gears, noticeable delays when shifting, particularly during acceleration or deceleration.
  • Solution: In some cases, a software update to the transmission control module (TCM) may resolve the issue. In more severe cases, valve body replacement or complete transmission replacement may be necessary.
  • Estimated Cost to Fix: $300 for software update, $2,000 - $5,000+ for valve body/transmission replacement.
• Torque Converter Issues
  • Description/Symptoms: Shuddering or vibrations at low speeds, especially during light acceleration. Can also cause stalling or difficulty shifting.
  • Solution: Replacement of the torque converter.
  • Estimated Cost to Fix: $1,500 - $3,000+

Suspension

• Air Suspension Malfunctions (If Equipped)
  • Description/Symptoms: Vehicle leaning to one side, ride height not adjusting properly, error messages on the dashboard related to the air suspension system.
  • Solution: Diagnosis and repair of the air suspension system, potentially including replacement of air struts, air compressor, or ride height sensors.
  • Estimated Cost to Fix: $800 - $2,000+ per air strut, $500 - $1,000+ for compressor.

Electrical

• Infotainment System Glitches
  • Description/Symptoms: System freezing, crashing, or becoming unresponsive. Bluetooth connectivity issues, navigation problems, and display malfunctions.
  • Solution: Software updates, system resets, or, in some cases, replacement of the infotainment system.
  • Estimated Cost to Fix: $0 - $100 for software updates, $1,000+ for system replacement.
• Sensor Failures (Parking Sensors, Blind Spot Monitoring)
  • Description/Symptoms: Malfunctioning parking sensors, inaccurate readings, false alarms, or complete failure. Blind spot monitoring system not working correctly.
  • Solution: Replacement of the faulty sensor(s).
  • Estimated Cost to Fix: $200 - $500+ per sensor.
• Battery Drain
  • Description/Symptoms: Car battery draining overnight or within a short period of time, difficulty starting the engine, and needing to jump-start the vehicle frequently.
  • Solution: Diagnosis and repair of the parasitic drain. This could involve replacing a faulty module or fixing a wiring issue.
  • Estimated Cost to Fix: $100 - $500+ depending on the cause.

Exterior

• Sunroof Issues
  • Description/Symptoms: Sunroof not opening or closing properly, getting stuck, or making excessive noise during operation. Water leaks around the sunroof seal.
  • Solution: Repair or replacement of the sunroof mechanism or motor. Cleaning and resealing the sunroof frame.
  • Estimated Cost to Fix: $300 - $1,000+

Interior

• Seat Heater Malfunction
  • Description/Symptoms: Seat heaters not working, only partially heating, or overheating.
  • Solution: Replacement of the heating element or control module.
  • Estimated Cost to Fix: $300 - $800+ per seat.
• Dashboard Creaks/Rattles
  • Description/Symptoms: Annoying creaking or rattling noises coming from the dashboard, particularly when driving on uneven surfaces.
  • Solution: Identifying the source of the noise and tightening loose components or adding padding to prevent friction.
  • Estimated Cost to Fix: $100 - $500+ depending on the complexity.

Recalls: None Found

The 2021 Mercedes-Benz C300, while a generally well-regarded luxury sedan, has exhibited some common issues. Engine problems like camshaft adjuster and high-pressure fuel pump failures can be costly to repair, as can transmission problems like rough shifting. Electrical gremlins, such as infotainment glitches and sensor failures, also appear frequently. The severity of these issues ranges from minor inconveniences to major mechanical problems. While some repairs, such as software updates, are relatively inexpensive, others, such as engine and transmission replacements, can run into the thousands of dollars.