What 38 owners told NHTSA about the 2020 Mercedes-benz GLS

On numerous occasions the transmission does not fully down shift to the next lower gear and then when I have to accelerate quickly it will drop down to the lower gear like it’s supposed to but won’t shift out to the next higher gear and when I let my foot off the accelerator the truck slows down quickly like applying the brakes which almost had me rear ended a few times and now the adaptive cruise control is malfunctioning

NHTSA ODI 11653819

This incident occurred around 5:50pm on Wednesday, September 21, 2022. I was driving on a merge connector between two freeways in San Francisco at about 60mph, when the vehicle threw a series of error codes and warnings on its displays, culminating with “shut down engine immediately”. The first error was a 48V battery system charging failure, and the second was a warning that coolant was too hot. The instrument panel and steering and brakes did not lose power, but the accelerator no longer worked, and the vehicle slowed down to about 35mph. I had to merge across 4-5 lanes of rush hour traffic at this speed (sketchy) to make it to the side of the freeway, and was able to exit safely and stop in a safe spot. Upon turning off the vehicle for a few minutes and then restarting it, a generic check engine light remained on afterwards. I had the vehicle towed to a Mercedes dealer where the fault(s) are currently being diagnosed. According to the dealer, they are in touch with MBUSA Engineering due to the nature of the fault codes. The vehicle had recently undergone a 50,000 mile routine service without any problems being flagged. The safety implications of this incident are clear: with no ability to match the speed of the flow of traffic, I could have been rear-ended or involved in a collision as I limped across the freeway to safety. I am fortunate that the vehicle had enough residual kinetic energy that I didn’t end up stuck blocking a freeway lane in rush hour traffic. Searching online for similar issues, this appears to be a known manufacturing issue with the mild hybrid inline-6 engine in this model of vehicle. For instance, all of the top Google hits for the term “GLS 48V battery failure” yield relevant and similar reports from other drivers, including summaries from consumer lawyers like this one: https://lemberglaw.com/mercedes-benz-gle-battery-electric-problems/

NHTSA ODI 11486139

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 an started the vehicle. I have had passengers in the vehicle who will attest to this occurring, in fact, the last time it happened, I 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. When I called MB Customer Service, Michael (initial intake) told me "I have seen this issue before."

NHTSA ODI 11465253

We were driving the vehicle at about 30 MPH on a road when suddenly the engine completely shut off. There was no more power steering and no warning that it turned off. We got the car slowed down and once we came to a stop the car put itself in Park. After that we could restart it and keep driving with the car acting very different. This then happened again later on in the day going about 20 MPH up to a stop light. It shut itself off and luckily we were able to come to a stop with the brakes without running into the intersection and no one hitting us from behind. Once again it put itself in Park. We were able to restart the car and drive again with diminished power and really weird shifting from the transmission. The check engine light turned on both times and when we got it to the dealership the next morning all the check engine lights were off again. This is extremely dangerous to the driver and occupants. Our little son was in the back seat. We commute with this car in southern california and if this were to happen on the freeway it would be disastrous. Everyone is at risk with this car. It will just stop without any warning signs and you can have someone rear end you. And the power steering turns off also which if the car turns off in a corner on the freeway you will have no way of controlling the vehicle and will just go into the middle barrier or oncoming traffic. This could be even worse if driven on a mountain road and you loose all power of the vehicle. We will not be driving the car anymore since we have no idea when it will shut off again while driving.

NHTSA ODI 11427911