2021 Mercedes-Benz S-Class Problems: 1 Issues Every Owner Should Know
2021 model year · 600+ owner reports · Updated April 2026
According to Au7o's analysis of 600+ owner reports, the 2021 Mercedes-Benz S-Class has 1 documented known issues. No issues are rated critical, indicating generally reliable ownership. The most commonly reported issue is 48V Mild Hybrid Battery Issues with 600 owner reports. Across all issues, repair costs range from $200 to $3,000. DIY maintenance guides at au7o.io.
All 1 Known Issues
On the 2021-2025 Mercedes-Benz S-Class, the 48V EQ Boost mild hybrid system battery degrades or fails prematurely, triggering multiple warning messages and disabling the start-stop, electric boost, and regenerative braking functions. Software glitches also cause false battery fault warnings.
Common Symptoms
- Multiple electrical warning messages on dashboard
- Start-stop system disabled
How to Fix
Have the dealer diagnose with XENTRY to differentiate between a software fault and genuine battery failure. Update to the latest software calibration. If the 48V lithium-ion battery has failed, replacement runs $1,500-3,000 at the dealer.
What Owners Are Using
Parts and tips from 600+ owners who fixed this issue
- TipRequest the latest XENTRY software update before approving a battery replacement. Many 48V fault codes are resolved by software calibration alone.