Owner-reported issues — NHTSA
154 complaints filed with the National Highway Traffic Safety Administration for the X166 across model years 2015–2020. Federal public records, updated weekly.
| UNKNOWN OR OTHER | 36 reports |
| STEERING | 18 reports |
| ENGINE | 18 reports |
| SERVICE BRAKES | 13 reports |
| SEAT BELTS | 13 reports |
| AIR BAGS | 10 reports |
| STRUCTURE | 10 reports |
| FUEL/PROPULSION SYSTEM | 8 reports |
Selected owner reports
2015 · STEERING
I loss my electric steering assist!!! Takes 2 gorillas to turn the wheel i was able to stop without crashing into anything
2015 · FUEL SYSTEM
The contact owns a 2015 Mercedes-Benz S550. The contact stated that while driving approximately 45 MPH and approaching a stop, the vehicle experienced a loss of automotive power. Several unknown warning lights were illuminated. There was an abnormal ticking sound coming from the engine, and the brakes squeaked while turning. While refueling the vehicle, there was fuel leaking from the vehicle. The contact stated that while driving and attempting to stop, the brake pedal was depressed and felt loose, and the vehicle hesitated while coming to a stop. The vehicle was restarted and taken to a loca
2015 · AIR BAGS
The contact owns a 2015 Mercedes-Benz S550. The contact stated that while operating the vehicle, the air bag warning light remained illuminated, with the message "Front Drivers Air Bag Malfunction - Service Required" displayed. The cause of the failure was not yet determined. The manufacturer and local dealer were notified of the failure, but no assistance was provided. The contact was informed that the VIN was not included in NHTSA Campaign Number: 17V177000 (ELECTRICAL SYSTEM, AIR BAGS). The contact stated that the vehicle had experienced the failure listed in the recall. The failure mileage
2015 · WHEELS
Brought my vehicle to my mechanic because of noise that recently appeared in my car. To my surprise the mechanic stated that my engine is completely failing and would require an entire new engine. I purchased this car less than two years ago with an estimated 79,000 miles. Vehicle currently has an estimated 112,000 miles. Never missed a service interval for the vehicle. Now several components of the engine are completely failing.
2015 · STRUCTURE
Roof panel between windshield and panoramic sunroof has developed fine hairline fractures on the polycarbonate panel. Why wasn't my vehicle included in recall 21V-197? Thanks for your time.
2015 · STEERING
The steering wheel became difficult to control.Also,steering wheel module waring light came on.
2015 · SEAT BELTS
The rear seatbelts do not retract to restrain the passenger. They also don't retract after the passenger has exited the vehicle.
2015 · ENGINE
Cylinder wall 2 and 3 scorn horribly. Coolant leaking into cylinder 2 & 3. Dealer recommendation of new motor due to bad block. German Auto Works and CarStoreUSA Wichita KS both recommend new motor and have advised of many of same motors being recalled by Mercedes Benz. I also spoke with Mercedes Benz North America. The heads were replaced in 2022 already and have under 10k miles on motor since repair.
2015 · SUSPENSION
The contact owns a 2015 Mercedes-Benz S550. The contact stated while driving at an undisclosed speed, the contact noticed a squeaking sound coming from the undercarriage of the vehicle. The vehicle was taken to the dealer where it was diagnosed with suspension strut spring control arm joint. The contact was informed that the suspension strut spring control arm joint needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure but provided no assistance. The contact was advised to contact the NHTSA Hotline to report the failure. The failure mileage was app
2015 · SEAT BELTS
The contact owns a 2015 Mercedes-Benz S550. The contact stated that the rear driver's side seat belt was inoperable. The contact stated that the seat belt failed to retract as designed. The vehicle was taken to the dealer where it was diagnosed with a failed seat belt retractor. The contact was informed that the seat belt retractor needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and the contact was advised to contact the NHTSA Hotline to report the failure. The failure mileage was approximately 75,000.
2015 · STRUCTURE
The driver side reader door can be opened when the door is locked. The door can be inspected on request. The risk is that the door can be opened when the door is indicated as locked. There are no lights to the contrary. The car is inspected by Mercedes dealer at McFarland in Georgia. See Mercedes recall Campaign 2018010009, March 2018.
2015 · SEAT BELTS
Rear passenger seat belt will not retract. Has done twice before and took weeks before retracting by itself.
Source: NHTSA consumer complaint database · synced 2026-09-07