AI Damage2020 Mercedes-Benz SLC 300 reliability: common problems
Owners of the 2020 Mercedes-Benz SLC 300 filed 1 complaints with NHTSA, most often about electrical system. The maker issued 81 service bulletins for this year. We found 1 repair videos on YouTube. Details by component below, with sources.
Key figures
- Owner complaints
- 1
- Technical service bulletins (TSB)
- 81
- YouTube repair videos
- 1
What fails most often
- Electrical system: 1 complaints (100% of all); manufacturer bulletins for this component: 13.
Components owners complain about
| Component | Owner complaints | involving a crash | Technical service bulletins (TSB) |
|---|---|---|---|
| Electrical system | 1 | 0 | 13 |
| Powertrain | 0 | 0 | 23 |
| Exterior lighting | 0 | 0 | 13 |
| Engine | 0 | 0 | 9 |
| Engine and cooling | 0 | 0 | 7 |
| Equipment | 0 | 0 | 7 |
| Structure | 0 | 0 | 6 |
| Steering | 0 | 0 | 4 |
| Visibility | 0 | 0 | 3 |
| Suspension | 0 | 0 | 2 |
| Fuel system | 0 | 0 | 1 |
| Latches, locks, linkages | 0 | 0 | 1 |
| Seats | 0 | 0 | 1 |
| Service brakes | 0 | 0 | 1 |
Comparison
By complaint count this model year ranks 21,984 of 32,257 model years in the NHTSA data (among the 32% least complained about).
On average one model year of the SLC 300 has 1 complaints (5 years in the data). This year has 1, below average.
What to check before buying
- Electrical system. Scan all modules, test the battery and alternator, inspect connectors near the impact zone.
- Powertrain. Shift quality under load, harsh shifts, transmission codes, CV joints.
- Exterior lighting. Headlamps, leveling, sensors and mounts after a frontal hit.
- Engine. Cold start, unusual noises, oil leaks and engine codes.
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 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 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…
- Complaint This document is intended as a pre-case diagnostic reference for transmission related concerns
It will also ensure that if a case is necessary, all supporting documentation is available. This should not be used on its own as justification for creating a TIPS case. Cause The root cause will vary depending on the…
- Complaint Mercedes-Benz USA is currently experiencing limited availability of transmission fluid…
Complaint Mercedes-Benz USA is currently experiencing limited availability of transmission fluid specification ATF 236.17 due to a global supply constraint. 236.17 ATF 1L and 5L (PNs: A002989060312 and A002989060313)…
- Single throttle lift-off clunking noise from the side shaft when moving off (audible at the outboard end)
The noise is heard once in each instance when changing direction of travel. Note: Sound file in attachment Cause If the complaint is eliminated by experimentally loosening the outboard collar nut (by 1 turn), the…
- Complaint After successful commissioning of the HERMES control unit (N112/9) with XENTRY Diagnosis DVD…
Complaint After successful commissioning of the HERMES control unit (N112/9) with XENTRY Diagnosis DVD 03/2026, the message "SOS - service not activated" appears on the instrument cluster. In addition, the following…
- Dear Mercedes-Benz USA Dealers, The part numbers listed in the chart below should no longer be installed,…
Dear Mercedes-Benz USA Dealers, The part numbers listed in the chart below should no longer be installed, and any existing stock must be returned to your facing PDC. The deadline for all dealer returns is no later than…
- Complaint The customer requests deactivation of the N112/9 HERMES communication module Note
Deactivation of the HERMES control unit (N112/9) is not supported for gray-market vehicles. Cause Before deactivating the HERMES control unit (N112/9), it must be clarified by the legal department of the respective MPC…
NHTSA lists 81 bulletins for this year; the 12 newest are shown here.
Repair videos
We do not copy videos: these are YouTube links credited to their authors. Amounts are as stated by the author and not verified by us.
Other years of this model
Questions and answers
What are the most common problems with the 2020 Mercedes-Benz SLC 300?
Owner complaints to NHTSA most often mention: electrical system. Total complaints: 1.
How many service bulletins (TSB) were issued for the 2020 Mercedes-Benz SLC 300?
NHTSA lists 81 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 2020 Mercedes-Benz SLC 300 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 2020 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.