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What 36 owners told NHTSA about the 2021 Mercedes-benz GLS

These are the actual owner complaints behind this car’s reliability verdict, filed with the federal government, unedited. They’re unverified reports, not confirmed defects: read them as leads for your pre-purchase inspection, not a diagnosis.

All (36)Crash / fire / injury (5)Electrical system (16)Engine (4)Driver assistance (3)Lane Departure (3)Fuel system (2)Seats (2)Visibility & wipers (2)Airbags (1)Body & structure (1)Seat belts (1)

3 of 36 complaints match · Driver assistance · clear filters

Jan 9, 2023EngineDriver assistanceLane Departure

On four occasions my car has stalled while in traffic very early in my ownership and then it happened again today with my family in the car and nearly caused an accident. The entire dash lights up with every warning when it happens. Sometimes the check engine light comes on after I shut the car off and restart it. My Mercedes dealer has had it in multiple times for this reason. The last time it was in for this (May of 2022) they "reprogrammed" the entire car. It happening again today has really made me lose a lot of faith in the vehicle, especially since we purchased it for the safety factors. I read online that there are many others who have experienced this. Some say it is related to the 48V battery. I don't care what Make or Model or how expensive it is, a new car should NOT stall in traffic and should be looked into. Thank You.

NHTSA ODI 11500946

Jul 28, 2021Driver assistance

The contact owns a 2021 Mercedes-Benz GLS63. The contact stated while driving at various speeds, the collision warning sensor was activated with an audio alarm and warning on the display screen. The contact stated that there were no objects in the roadway or close to the vehicle. The contact stated that she had deactivated the driver assistance functions in the vehicle and the failure still occurred. The vehicle was not taken to the dealer or independent mechanic to be diagnosed nor repaired. The dealer was contacted and advised the contact to wash the vehicle. The contact stated that the vehicle was washed however, the failure persisted. The manufacturer was not notified of the failure. The approximate failure mileage was 200.

NHTSA ODI 11426863

Jul 26, 2021Speed controlDriver assistance

The contact owns a 2021 Mercedes Benz GLS450. The contact stated while driving 75 mph with the cruise control engaged, the vehicle decelerated to 45 mph than to 15 mph. On another occasion, while driving 80 mph, the vehicle independently decelerated to 45 mph. There was no warning light illuminated. The vehicle was taken to the local dealer however, the mechanic was unable to duplicate the failure. The vehicle was not diagnosed nor repaired. The contact stated that the cruise control and speed assistance feature provided erroneous information. The manufacturer was notified of the failure. The failure mileage was 3,000.

NHTSA ODI 11426426

Working with the data? Download all 36 complaints as CSV · fetched from NHTSA July 20, 2026

How to use these: a complaint is one owner’s report, filed voluntarily and published unverified. Patterns matter more than any single story. If several owners describe the same failure at similar mileage, put that system at the top of your pre-purchase inspection list. Back to the full 2021 Mercedes-benz GLS verdict →