2020 Mercedes Benz GLS Problems and Top Complaints – Is Your Car A Lemon?

Battery & Engine issues are among the top complaints received by the NHTSA from vehicle owners

Updated on Author: Brian Jones

The Mercedes-Benz GLS SUVs are lightweight (leicht), cross-country vehicles (gelandewagen). That’s where the G and L come from. The S stands for special class (sonderklasse).

The GLS has been around since 2006 when it joined the Mercedes-Benz lineup as the brand’s first 7-passenger SUV. A highlight of the second generation was its innovative engine start/stop system, called ECO-START. The third generation, introduced in 2020 offered two powerful engine options and a bunch of new features.

But complaints about the 2020 GLS-Class SUV are mounting up. There are currently 11 complaints to the U.S. Department of Transportation’s National Highway Traffic Safety Administration (NHTSA). Of these, 7 are listed as electrical system problems and 6 as fuel/propulsion system issues. A total of 4 are seen as engine problems and there are also 2 complaints about the powertrain. There is 1 complaint each about seats, steering, and another listed in the Unknown or Other category.

Click on other model year to view more problems: 2021

The Most Common Problems

The most common problem with the 2020 Mercedes-Benz GLS-Class SUV is its 48-volt batteries.

2020 Mercedes Benz GLS Complaint Summary

Complaint CategoryNumber of Complaints
Electrical System
Fuel/propulsion System
Power Train
Forward Collision Avoidance: Automatic Emergency Braking
Unknown Or Other
Air Bags
Back Over Prevention: Warnings
Service Brakes

Battery Issues

Nearly half the complaints to NHTSA relate to battery problems

Lemberg Law is currently investigating complaints about Mercedes-Benz GLE battery problems. From complaints we have identified about other models, it might be a much broader issue. For example, we are aware that there are at least three technical service bulletins (TSBs) that Mercedes-Benz has issued about the 48V battery problems, but only one is officially linked to the 2020 GLS. This states that the cause might be software or hardware issues.

Battery Issue is a life-threatening problem

The owner of a GLS SUV with a battery issue believes it is “a LIFE-THREATENING DANGEROUS VEHICLE PROBLEM,” especially because the problems keep recurring.

The first time, the engine turned off and the car wouldn’t accelerate. Once this happened on a busy freeway.

“In this instance, the 48-volt battery failure warning, engine overheat warning, engine light warning came on. When MCB dealership evaluated the vehicle, there were no stored associated error codes and MCB service returned the vehicle to me saying that the issue did not occur when they drove it.

“The same issue occurred again 5 months later, this time in a busy intersection, where the car would not accelerate and I was forced to pull off the road. The check engine light as well as other failure lights came on. The car was returned to MCB service and again, no error codes were stored and the dealership said they could not find the cause of the problem.”

This owner is convinced the problem “could easily result in a catastrophic accident.” Additionally, “Mercedes is taking no accountability for this vehicle failure and claims they have not heard of this issue prior, which is clearly inaccurate given that it has been reported to NHTSA by several other GLS owners.”

Other similar complaints echo how dangerous the issue is

“In looking at the issue online this appears to be a known problem to Mercedes. They are even facing a class action lawsuit for it in the same model year GLE, which is based on many of the same systems. Someone is going to get killed when their vehicle stalls in the middle of the highway.”

After being told there was a 48V battery malfunction, another owner was warned not to drive the vehicle “under any circumstances.”

“This is a serious issue and it appears that changing the battery does not correct the issue.”

An owner who shipped a new 2020 Mercedes-Benz 450 from Oakland to Hawaii complains that the failure happened about 4,100 miles. “We experienced a 48 volt battery malfunction which left our car disabled on the side of an uphill major roadway. There was no warning, just a sudden extreme loss of power. Supplemental systems such as the AC deactivated. Warning lights flashed and our vehicle coasted to the side of the road.”

The owner wasn’t able to accelerate and there were over-heating warnings in red.

“We are very concerned (that) this malfunction is a safety-related issue and needs to be escalated. Sudden unexpected loss of power creates extremely dangerous situations.”

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Engine Problems

Engine problems relate to the engine dying or shutting off.

An owner from Virginia has found that “on numerous occasions, when either slowing down or in a slow turn, the engine dies and will not reengage until I have turned off the vehicle, exited, then reentered and started the vehicle.’

Offering passengers as witnesses, the owner says the SUV was “almost broadsided when the vehicle stopped in the middle of a left-hand turn, crossing three lanes of oncoming traffic. The vehicle has been to the dealership at least three times and it’s either a ‘software update’ requirement or ‘we can’t duplicate’ the issue.”

However, the owner was also told by someone in customer services, “I have seen this issue before.”

Fuel/Propulsion Issues

Some of the fuel/propulsion complaints are linked to battery problems. But one quite different one relates to the catalytic converter. First, the owner noticed fuel odors and then abnormal noises that sounded like explosions. At this point, the dealer diagnosed the problem and said the catalytic converter and turbo had to be replaced. The failure mileage was only 1,000.

What to do if Your 2020 Mercedes Benz GLS is a Lemon? Your Lemon Rights

When problems recur or affect the use, value, or safety of your vehicle, there’s a possibility that you’re sitting with a lemon. But you don’t have to live with it. If you think you may have a lemon, why not let Lemberg Law assess your case.

We have negotiated numerous settlement deals for our clients and initiated many class-action suits. It won’t cost you anything because legally, Mercedes-Benz must pay all the legal fees of lemon law cases.

Brian Jones

About the Author:

Brian Jones spent more than 30 years working as an ASE Certified Master Tech and Parts Specialist at multiple dealerships. Brian has become an authority in the industry, traveling across the country to consult for car dealerships and contributing his expertise as a writer for several major automotive publications. In his spare time, Brian enjoys working on pickup trucks, muscle cars, Jeeps and anything related to motorsports.

See more posts from Brian Jones

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