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Mercedes-Benz · Known Issues

2020 Mercedes-Benz CLS-Class Problems & Issues

2020 model year · NHTSA recalls, manufacturer TSBs, and owner forum reports · Updated September 2026

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Issue summary

According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 2020 Mercedes-Benz CLS-Class has 4 documented known issues, with 1 rated critical. The most serious is 48-Volt Integrated Starter-Generator / DC-DC Converter Failure Causing Warning Messages, Limp Mode, or No Restart ($1,200-$6,500 repair). Across all issues with published estimates, repair costs range from $100 to $6,500. DIY maintenance guides at au7o.io.

In This Article

  • CLS-Class Electrical2
  • CLS-Class Body/Panels1
  • CLS-Class Brakes1
  • FAQ
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In This Article

  • Electrical2
  • Body/Panels1
  • Brakes1
  • FAQ

All 4 Known Issues

Filter:
ALL YEARS20242023202220212020201920182017201620152014201320122011201020092008200720062005

When Issues Typically Appear

MBUX / Instrument Cluster Software Freezes, Black Screens, and Backup Camera Malfunctions
0K-80K
Panoramic Sunroof Creaking, Popping, or Binding from Glass/Frame Adjustment and Seal Friction
5K-70K
48-Volt Integrated Starter-Generator / DC-DC Converter Failure Causing Warning Messages, Limp Mode, or No Restart
10K-70K
Front Brake Squeal and Premature Rotor/Pads Wear on AMG-Line and AMG Variants
10K-50K
025K50K75K100K mi

On the 2019-2024 Mercedes-Benz CLS-Class 3.0L turbo I6 M256, owners of six-cylinder CLS 450 models have reported failures in the 48V mild-hybrid system, including the integrated starter-generator, 48V battery support components, or DC-DC converter. Symptoms include 'Stop Vehicle Leave Engine Running,' multiple warning lights, loss of charging support, disabled start/stop, reduced power, and in some cases inability to restart after shutting the car off. This issue is well documented across Mercedes models using the M256/48V architecture and appears in owner complaints and service literature.

This issue also affects: Mercedes-Benz C-Class, Mercedes-Benz E-Class, Mercedes-Benz AMG GT 4-Door

Common Symptoms

  • 48V battery malfunction warning
  • stop vehicle leave engine running message
  • multiple warning lights
  • vehicle will not restart
  • loss of start-stop function
  • reduced power
  • battery not charging

How to Fix

Perform a full scan of both 12V and 48V systems with Mercedes-capable diagnostics, checking charging voltage, converter operation, and fault memory in the powertrain and energy management modules. Repairs vary by root cause but commonly involve replacing the DC-DC converter, 48V battery, wiring, or the integrated starter-generator assembly, followed by software updates and battery registration/adaptation. Because the system is safety-critical and high-voltage relative to standard 12V systems, diagnosis is best handled by a Mercedes specialist or dealer.

Owner tips & cautions

  • TipDo not keep driving on repeated 48V warnings; low converter output can cascade into 12V undervoltage faults and strand the car.
Typical repair cost:$1,200 - $6,500

Research This Issue

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Community Reported
High Confidence

On the 2019-2024 Mercedes-Benz CLS-Class, current-generation CLS models use the widescreen MBUX infotainment and digital cluster system, and owners have reported intermittent screen blackouts, frozen displays, reboot loops, inoperative audio/navigation, and backup camera image failures. Mercedes has issued multiple software updates and service guidance for MBUX-related glitches across this platform. While often software-related, some cases involve display, camera, or control unit replacement when updates do not resolve the issue.

This issue also affects: Mercedes-Benz AMG GT, Mercedes-Benz C-Class, Mercedes-Benz E-Class

Common Symptoms

  • center screen goes black
  • instrument cluster freezes
  • backup camera not available
  • system reboots repeatedly
  • navigation or audio unavailable
  • touchpad or steering wheel controls unresponsive

How to Fix

Check for stored communication and infotainment faults, verify software level, and apply the latest Mercedes head-unit/instrument cluster updates. If the concern includes a blank reverse camera or persistent black screen, inspect LVDS/video connections, camera module operation, and power/ground integrity before replacing hardware. Battery voltage should also be tested because low system voltage can trigger false MBUX faults.

Owner tips & cautions

  • TipAsk the dealer to document current software versions before approving expensive hardware replacement; many cases are fixed by programming.
Typical repair cost:$150 - $2,500

Research This Issue

GoogleRedditYouTubeNHTSA
Community Reported
High Confidence

On the 2019-2024 Mercedes-Benz CLS-Class, a recurring owner complaint on the C257 CLS is noise from the panoramic roof area, especially over driveways, uneven pavement, or in hot/cold weather. The problem is usually not shattered glass but creaking or popping caused by seal friction, roof panel adjustment, or frame movement. Mercedes service departments commonly address it with lubrication, seal treatment, and roof alignment procedures, though some cars need repeat visits.

This issue also affects: Mercedes-Benz GLB, Mercedes-Benz GLC

Common Symptoms

  • creaking from roof area
  • popping noise over bumps
  • noise worse in temperature changes
  • sunroof feels tight or binds
  • intermittent rattles above front seats

How to Fix

Road-test the vehicle over low-speed body-twist conditions to isolate the roof from interior trim noises. Clean and condition the roof seals, inspect tracks and panel alignment, and perform factory adjustment procedures for the glass and frame if needed. If noise persists, inspect for loose fasteners or worn guide components in the roof cassette.

Owner tips & cautions

  • TipMany owners report temporary improvement after cleaning and treating the roof seals with a Mercedes-approved rubber care product.
Typical repair cost:$100 - $1,800

Research This Issue

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Community Reported
Medium Confidence

On the 2019-2024 Mercedes-Benz CLS-Class 3.0L turbo I6 M256, owners of CLS models with larger sport brake packages, especially CLS 450 AMG Line and AMG CLS 53, frequently report persistent front brake squeal, groan at low speeds, and faster-than-expected pad/rotor wear. In many cases the brakes still function normally, but noise and rotor scoring lead to repeated dealer visits. This is a common real-world complaint on Mercedes performance-oriented brake setups using aggressive pad compounds.

Common Symptoms

  • front brake squeal
  • groaning at parking-lot speeds
  • brake dust buildup
  • rotor scoring
  • steering wheel vibration under braking

How to Fix

Inspect pad thickness, rotor runout, rotor surface condition, and caliper slide/piston operation. Mercedes dealers often apply updated pad shims, anti-squeal compound, bedding procedures, or replace pads/rotors if glazing or scoring is present. Using OE-spec friction materials and proper bedding is important; cheap aftermarket pads often worsen noise or dust.

Owner tips & cautions

  • TipIf the brakes squeal after recent service, ask whether the pads were properly bedded and whether anti-squeal paste/shims were installed.
Typical repair cost:$400 - $2,200

Research This Issue

GoogleRedditYouTubeNHTSA
Community Reported
Medium Confidence
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Frequently Asked Questions

What are the most common Mercedes-Benz CLS-Class problems?

According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 2020 Mercedes-Benz CLS-Class has 4 documented issues. The most frequently reported are: 48-Volt Integrated Starter-Generator / DC-DC Converter Failure Causing Warning Messages, Limp Mode, or No Restart, Panoramic Sunroof Creaking, Popping, or Binding from Glass/Frame Adjustment and Seal Friction, MBUX / Instrument Cluster Software Freezes, Black Screens, and Backup Camera Malfunctions. Of these, 1 is rated critical and should be addressed promptly.

Is the Mercedes-Benz CLS-Class reliable?

The 2020 Mercedes-Benz CLS-Class has 4 known issues compiled from NHTSA recalls, manufacturer TSBs, and owner forum reports. 1 issue is rated critical: 48-Volt Integrated Starter-Generator / DC-DC Converter Failure Causing Warning Messages, Limp Mode, or No Restart. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common Mercedes-Benz CLS-Class problems?

Repair costs for known Mercedes-Benz CLS-Class issues range from $100 to $6,500, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, 48-Volt Integrated Starter-Generator / DC-DC Converter Failure Causing Warning Messages, Limp Mode, or No Restart, typically costs $1,200-$6,500 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 2019-2024 Mercedes-Benz CLS-Class 48-Volt Integrated Starter-Generator / DC-DC Converter Failure Causing Warning Messages, Limp Mode, or No Restart?

Owners of six-cylinder CLS 450 models have reported failures in the 48V mild-hybrid system, including the integrated starter-generator, 48V battery support components, or DC-DC converter. Symptoms include 'Stop Vehicle Leave Engine Running,' multiple warning lights, loss of charg… Repairs typically run $1,200-$6,500. Severity: high.

What is the 2019-2024 Mercedes-Benz CLS-Class Panoramic Sunroof Creaking, Popping, or Binding from Glass/Frame Adjustment and Seal Friction?

Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.

Data compiled from NHTSA recalls, manufacturer TSBs, automotive forums, and AI-assisted research. No aggregated owner-report counts available for this vehicle yet.

A recurring owner complaint on the C257 CLS is noise from the panoramic roof area, especially over driveways, uneven pavement, or in hot/cold weather. The problem is usually not shattered glass but creaking or popping caused by seal friction, roof panel adjustment, or frame movem… Repairs typically run $100-$1,800. Severity: medium.

What is the 2019-2024 Mercedes-Benz CLS-Class MBUX / Instrument Cluster Software Freezes, Black Screens, and Backup Camera Malfunctions?

Current-generation CLS models use the widescreen MBUX infotainment and digital cluster system, and owners have reported intermittent screen blackouts, frozen displays, reboot loops, inoperative audio/navigation, and backup camera image failures. Mercedes has issued multiple softw… Repairs typically run $150-$2,500. Severity: medium.

What is the 2019-2024 Mercedes-Benz CLS-Class Front Brake Squeal and Premature Rotor/Pads Wear on AMG-Line and AMG Variants?

Owners of CLS models with larger sport brake packages, especially CLS 450 AMG Line and AMG CLS 53, frequently report persistent front brake squeal, groan at low speeds, and faster-than-expected pad/rotor wear. In many cases the brakes still function normally, but noise and rotor… Repairs typically run $400-$2,200. Severity: medium.