Mercedes-Benz · Known Issues
2021 Mercedes-Benz GLS Problems: 17 Known Issues
2021 model year · 3,550+ owner reports · Updated September 2026
2021 · All trims · All engines
Choose the year and equipment for your written issues and visual request.
2021 model year · 3,550+ owner reports · Updated September 2026
2021 · All trims · All engines
Choose the year and equipment for your written issues and visual request.
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According to Au7o's analysis of 3,550+ owner reports, the 2021 Mercedes-Benz GLS has 17 documented known issues, with 5 rated critical. The most serious are AIRMATIC Air Suspension Failure ($800-$4,000 repair), 48V Ground Connection Overheating and Fire Risk (Recall 24V207) ($0-$0 repair), 4MATIC Transfer Case Bearing Wear, Whine and Drivetrain Lock-Up Risk ($2,500-$7,000 repair), Engine Stall from Transmission Control Unit Software (Recall 24V118) and Fuel Pump Impeller Deformation Causing Pump Shutdown and Loss of Drive Power (Recalls 23V445 / 23V880) ($0-$1,800 repair). The most commonly reported issue is AIRMATIC Air Suspension Failure with 1,500 owner reports. Across all issues with published estimates, repair costs range from $100 to $9,000. DIY maintenance guides at au7o.io.
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According to Au7o's analysis of 3,550+ owner reports, the 2021 Mercedes-Benz GLS has 17 documented issues. The most frequently reported are: AIRMATIC Air Suspension Failure, 48V Ground Connection Overheating and Fire Risk (Recall 24V207), 4MATIC Transfer Case Bearing Wear, Whine and Drivetrain Lock-Up Risk. Of these, 5 are rated critical and should be addressed promptly.
The 2021 Mercedes-Benz GLS has 17 known issues documented across 3,550+ owner reports. 5 issues are rated critical: AIRMATIC Air Suspension Failure and 48V Ground Connection Overheating and Fire Risk (Recall 24V207) and 4MATIC Transfer Case Bearing Wear, Whine and Drivetrain Lock-Up Risk and Engine Stall from Transmission Control Unit Software (Recall 24V118) and Fuel Pump Impeller Deformation Causing Pump Shutdown and Loss of Drive Power (Recalls 23V445 / 23V880). 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.
Repair costs for known Mercedes-Benz GLS issues range from $0 to $9,000, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, AIRMATIC Air Suspension Failure, typically costs $800-$4,000 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
The GLS AIRMATIC system is prone to air spring leaks and compressor failure due to the vehicle's heavy curb weight (5,700+ lbs). Front air springs tend to fail first. The compressor overworks to maintain ride height and eventually burns out. Repairs typically run $800-$4,000. Severity: high.
On 48V mild-hybrid GLS 450/580 models, the ground cable bolt for the 48V system located under the front passenger seat may not have been tightened to specification at the factory. A loose ground lug increases electrical resistance which, combined with the very high currents the 4… Repairs typically run $0-$0. Severity: high.
The 4MATIC transfer case on the GLS is prone to internal bearing wear, typically beginning with fluid degradation or a slow leak from the output/case seals. As the bearings wear, owners report a whining or grinding noise that increases with vehicle speed and worsens over time. On… Repairs typically run $2,500-$7,000. Severity: high.
Recall 24V118 covers model-year 2020-2023 GLS 450 vehicles equipped with the six-cylinder gasoline engine and nine-speed transmission. If a 7th-to-6th downshift is not completed during slight braking while other conditions coincide, including low transmission-oil temperature and… Severity: high.
On 2021-2024 X167 GLS models (GLS 450, GLS 580, Maybach GLS 600 and AMG GLS 63), certain batches of the in-tank fuel delivery module were built with impellers whose plastic did not meet Mercedes' material specification. The impeller can swell and deform, drag against the pump hou… Repairs typically run $0-$1,800. Severity: high.
The 9G-Tronic nine-speed automatic exhibits harsh low-speed shifts and hunting between gears on inclines. The transmission software struggles to select the optimal gear among nine ratios, particularly noticeable in stop-and-go traffic. Repairs typically run $150-$2,500. Severity: medium.
The large panoramic sunroof on the X167 GLS develops water leaks at the drain tubes or seal interface. Water enters the headliner and can drip into the cabin, staining the headliner and potentially damaging the overhead electronics. Repairs typically run $100-$1,500. Severity: medium.
The 48V EQ Boost mild hybrid system causes excessive battery drain when parked. A software bug in the 48V battery management module fails to properly enter sleep mode, draining both the 48V lithium-ion and 12V lead-acid batteries. Repairs typically run $200-$3,500. Severity: medium.
The OM656 diesel uses a precise Bosch CP4 common-rail high-pressure fuel pump that reacts poorly to low-quality diesel or fuel contamination. Even minor tank impurities or a single mis-fueling event can damage the pump and injection nozzles, and metallic debris from a failing CP4… Repairs typically run $1,500-$8,000. Severity: medium.
Owners of GLS 450 models with the M256 3.0L turbocharged inline-six report elevated oil consumption that tends to surface at higher mileage (commonly reported around 60,000 miles / ~100,000 km). The pattern — oil disappearing without visible external leaks — points to internal pi… Repairs typically run $3,000-$9,000. Severity: medium.
Two software defects on early X167 GLS leave the driver without a backup-camera image, a FMVSS 111 violation. Under 21V-354 (May 2021), the MBUX communication-module software on 2020-2021 GLS 450, GLS 580, Maybach GLS 600 and AMG GLS 63 could leave the center display black or fro… Repairs typically run $0-$900. Severity: medium.
EU-market GLS 350d/400d models with the OM656 3.0L inline-six diesel suffer from sensitivity in the exhaust aftertreatment chain. The EGR (AGR) valve, diesel particulate filter (DPF) and SCR/AdBlue system are sensitive to poor fuel quality, short-trip driving and temperature swin… Repairs typically run $300-$2,500. Severity: medium.
On 2020-2022 GLE and GLS built at MBUSI Tuscaloosa, the chrome/black trim bars on the rear door windows were not fastened to specification during assembly. Under wind load at speed the bar can separate from the door and become a road hazard for following traffic. The initial Sept… Repairs typically run $0-$1,200. Severity: medium.
On 2020-2021 X167 GLS (GLS 450, GLS 580, Maybach GLS 600, AMG GLS 63) the evaporator drain hoses were not always seated to specification at the Tuscaloosa plant, so A/C condensate drains into the passenger compartment instead of under the car. Owners see soaked front carpets and… Repairs typically run $0-$1,500. Severity: medium.
A supplier production deviation meant the spring inside the left and right third-row seatback locking mechanism on 2020-2022 X167 GLS (GLS 450, GLS 580 and 2021 AMG GLS 63; about 59,574 vehicles) may not have been installed. Without the spring the latch does not hold the seatback… Repairs typically run $0-$0. Severity: medium.
GLS X167 owners report the MBUX infotainment system freezing, showing a black or flickering screen, distorted display, unresponsive touch controls, or randomly rebooting. The faults are intermittent and often software-related, frequently triggered by or persisting through OTA/sof… Repairs typically run $0-$600. Severity: low.
On 2020-2023 X167 GLS models with MB-Tex synthetic upholstery the driver and passenger front seat covers split open along the side bolster and thigh-support seams, often within the first two to three years and well under 40,000 miles. MBWorld owners report the driver seat going f… Repairs typically run $0-$1,500. Severity: low.
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.