AI Damage2021 Mercedes-Benz C 300 4matic: common problems
Owners of the 2021 Mercedes-Benz C 300 4matic filed 1 complaints with NHTSA, most often about powertrain and suspension. The maker issued 49 service bulletins for this year. Details by component below, with sources.
Key figures
- Owner complaints
- 1
- Technical service bulletins (TSB)
- 49
What fails most often
- 1 Powertrain 100% of all complaints
- 2 Suspension 100% of all complaints
- 3 Air bags 100% of all complaints
- Powertrain: 1 complaints (100% of all); manufacturer bulletins for this component: 12.
- Suspension: 1 complaints (100% of all); manufacturer bulletins for this component: 1.
- Air bags: 1 complaints (100% of all).
Components owners complain about
| Component | Owner complaints | involving a crash | Technical service bulletins (TSB) |
|---|---|---|---|
| Powertrain | 1 | 0 | 12 |
| Suspension | 1 | 0 | 1 |
| Air bags | 1 | 0 | 0 |
| Electrical system | 0 | 0 | 16 |
| Engine | 0 | 0 | 7 |
| Structure | 0 | 0 | 5 |
| Visibility | 0 | 0 | 5 |
| Exterior lighting | 0 | 0 | 2 |
| Fuel/propulsion system | 0 | 0 | 2 |
| Steering | 0 | 0 | 2 |
| Backover prevention | 0 | 0 | 1 |
| Lane departure | 0 | 0 | 1 |
| Seats | 0 | 0 | 1 |
| Service brakes | 0 | 0 | 1 |
What owners report
Short excerpts of NHTSA complaints in the original wording. These are owner statements not verified by NHTSA; personal data removed.
Driving and something came from underneath the vehicle and cause me to swerve in all the airbags deployed
Comparison
By complaint count this model year ranks 24,719 of 36,659 model years in the NHTSA data (among the 33% least complained about).
On average one model year of the C 300 4matic has 2 complaints (8 years in the data). This year has 1, below average.
What to check before buying
- Powertrain. Shift quality under load, harsh shifts, transmission codes, CV joints.
- Suspension. Wheel alignment, control arms, subframe, even tire wear.
- Air bags. Check the SRS light, stored codes and airbag/curtain status after any impact.
- Electrical system. Scan all modules, test the battery and alternator, inspect connectors near the impact zone.
Manufacturer service bulletins
Bulletin titles as filed with NHTSA.
- Complaint Clanking noise from the area of the speakers in the doors
Cause Under analysis. Remedy To narrow down the cause, first of all remove the door trim. • If the noise continues to occur even with the door trim removed, then continue the diagnosis working towards the speaker and…
- Complaint Slight creaking noises when steering
Cause Noises may come from one or more sleeves of the horn contact plate. Remedy Remove the horn contact plate and check the sleeves for noise; see attached video. If necessary, apply lubricant to the sleeves.
- Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic /9G‑TRONIC automatic…
Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic /9G‑TRONIC automatic transmission) and 725.1 (NAG3 facelift/9G‑TRONIC automatic transmission facelift) For faster, more effective and…
- Complaint Repeat workshop visit for vehicle vibration while braking from 60MPH. NOTE
Although the symptom is similar to a tire or wheel vibration, it is usually readily noticeable that it is distinctly different if it happens at all times or only while braking. Cause Although the cause of the vibration…
- Complaint Only vehicles with a variable transfer case are affected
This can be identified through control unit N45 or N15/7 in the quick test. When accelerating with light load, vibrations or jolting sensation may come from the drivetrain. It may be mistaken for a harsh shift. Cause…
- Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic / 9G‑TRONIC automatic…
Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic / 9G‑TRONIC automatic transmission) and 725.1 (NAG3 facelift/9G‑TRONIC automatic transmission facelift) For faster, more effective…
- Complaint CEL illuminates and/or AC does not blow cold
Cause Potentially relevance to hardware and/or software Remedy Scenario 1: 1. If the AC does not blow cold air, replace compressor (if compressor's index and part number Figure 1 match against Table 1). a. If the…
- Complaint During part of the steering movement, it feels heavier or more difficult to steer in the same…
Complaint During part of the steering movement, it feels heavier or more difficult to steer in the same spot every time. OR Rattling, humming, dry sliding/gravel noise from the electric steering system when steering…
- Dear Mercedes-Benz Owner
In our continuing efforts to ensure the proper performance of Mercedes-Benz products and to enhance the satisfaction of our customers, Mercedes-Benz USA is extending the warranty coverage for the Diagnostic Module for…
- Complaint Tailgate opens unintentionally
Cause Accidental or unnoticed activation of the button to open the tailgate on the vehicle key. EXAMPLE: when stored in trouser pocket, handbag etc. Remedy As of the 6th generation, the vehicle key can be recoded so…
- Complaint A popup is seen on the HU with the message "data connection temporarily not available"
Potentially affected functionalities in NTG4.5, NTG5 1.Weather 2.Local Search 3.IP Radio 4.Send2Car 5.Speech Detection Service 6.Navigation 7.iHeartRadio 8.Traffic Cams Cause MB Apps is sundowned for all vehicles with…
- Complaint 1
General Diagnostic Tips 2. One or More PARK Sensor Activations 3. Red Ring Around Vehicle 4. "Active Parking and Parking Assist Inoperative" on Instrument Cluster 5. Cameras 6. Other Park Topics. Cause Various root…
NHTSA lists 49 bulletins for this year; the 12 newest are shown here.
Other years of this model
Questions and answers
What are the most common problems with the 2021 Mercedes-Benz C 300 4matic?
Owner complaints to NHTSA most often mention: powertrain, suspension, air bags. Total complaints: 1.
How many service bulletins (TSB) were issued for the 2021 Mercedes-Benz C 300 4matic?
NHTSA lists 49 manufacturer service bulletins for this year. A bulletin tells dealers how to diagnose or fix a known issue; it is not a recall.
Should I buy a 2021 Mercedes-Benz C 300 4matic from a US auction?
Owner complaints describe defects, not crash damage. Before bidding, check the components listed above and review the lot photos: VinWind builds a report of visible and hidden damage by VIN.
Other 2021 models
Read also
Sources: public NHTSA data (USA): service bulletins and owner complaints; YouTube: links to videos credited to their authors. Complaints are owner statements not verified by NHTSA, and describe defects rather than crash damage. Data updated 2026-11-06.