So I hoped I would have owned this vehicle a little longer before I would have an issue with it. Let me just say that this is my first MB. It checks all my boxes that i wanted with a vehicle. Its perfect.. Until recently. I purchased this vehicle brand new in October 2017. In November I went to my garage and went to start it. I got in put my foot on the brake and pushed the button. The lights in the dash came on and the engine did a half crank (not even 1 full revolution and stopped). I thought it was just me and maybe my foot slipped off the brake pedal mid crank or something like that. I pushed the button again to put it to the off position and then tried it again and it started no problem. So i shrugged it off as my fault.... It has been fine all winter until a few weeks ago. Did the same thing in a parking lot. I thought to myself thats weird and this time I'm sure it was not my fault. I did however try to duplicate it with things like, pushing the button really fast or just tapping the brake pedal and then pushing the button really fast to see if i could replicate it. I could not.... Then a couple of days ago in the garage it became very clear that i was doing nothing wrong. It happened 4 times in a row before it actually started the engine. Each time i would push the button again to turn it off and then start the brake pedal and then push the button again sequence. It did the same 1/2 crank issue 4 times in a row and then on the 5 time it cranked like normal and its been fine ever since. I did not get a video of this issue as i was super frustrated at the time when this was happening and was late for an appointment. I have looked EVERYWHERE online trying to find someone with the same or similar issue with no luck.

I called the service manager at my local MB dealer (where i purchased it). I explained to him what was going on and obviously i got the "i haven't heard of that answer" which didn't surprise me as its an odd issue.. So we both agreed that i really can't bring it in until its pretty much dead in the water and won't start because they won't be able to fix it if its not happening at the time. I do have to say i agree with them completly and it would be a giant waste of everyones time to find out its fine for days while its there at the dealer. He did mention to me that the next time this happens to take a video. Which i will do. Also he wanted to me to take out the push to start button and use the key when this is happening to rule out the push to start system. I also agree with this.

So in closing has anyone heard of this? Oh BTW the car has 24,000 miles on it as of now. The rest of the vehicle has been perfect no other issues. I love this thing but I'm hoping that it doesn't leave me stranded someday..... Or it will be gone....

Thanks in advance and sorry for the winded post. Lot of information in there.


Adam

Hi!
I have the same problem with my GL 450, X166, Engine M278. Can you help me - what was the reason for your problem?

Unfortunately, the OP hasn't been back since a week after he made that post. Too bad when folks don't post the resolution.

There may be some failure codes stored that will tell why the start was aborted. Worth getting it scanned with a scanner that can read Mercedes specific data.

Replace the main and aux batteries on a 5+ year old MB, then go from there.

The main battery is brand new. I have a star diagnose - no any error in all of the modules. Just parked the car in front of my house. After 2 min I try to start and the engine cranked 1/2 and stoped. After this the starter just no trying to move. There is 12v on the starter relay and fuse.

What do you think is the most likely cause?

Engine blocked

Did you ever get this resolved. My car a 2018 GLS 450 just started doing this very same thing.

Are you able to scan it for codes?

I would check the 2 things first!
1) the relay to the stater motor
2) the starter motor

This situation happened to me on a VW diesel Jetta wagon. Turned out to be the brake light switch on the brake pedal was faulty. Intermittent signal loss would cause a no-start.
On the V-Dub it was a plunger-style switch mounted on the firewall between the brake pedal foot pad and the brake pedal pivot.