Nichts

Just bought my first MB. It had 22 miles on it at delivery, put on by me at the test drive. Now we're 3.5 weeks later and 1400 miles on, and this happens: Check Engine Light is on. Was driving on interstate at about 75 mph in Comfort mode, I fully stepped on accelerator to pass someone and when the engine kicked down, it felt like it missed the shift or something and the engine light started flashing and the vehicle lost power and went into Limp Mode. I coasted to the side of the road. I noticed the engine was running rough/vibrating the vehicle at idle. I parked and turned engine off. I made sure gas cap was on correctly (it was) and then I restarted it a few moments later and the CEL was off, and all engine function seemed normal. Continued on my way. When I got near my destination, I again pressed the accelerator fully to make sure it would kick down properly, and the car went back into Limp Mode, only this time the Check Engine Light remains on. The car seems to be running fine, though so I drove it home. Now, I am afraid to drive it ? Definitely not expecting this on a brand new MB.

I have a service appointment, but it's seven days away. Should I push for a loaner in the meanwhile? Anyone else have this? Honestly I'm very disappointed as this is my first luxury vehicle and I did the engine break-in period by the books.

chassis

Sorry to hear. Dealer needs to solve this. Please update the thread after the diagnosis.

Nichts

Will do. They scheduled me a week out. Hope it's nothing crucial or a safety risk of damaging the engine, but it seems to be fine aside from the CEL.

glassbloke

It’s a real safety issue if it goes into limp mode when you floor the accelerator. Did you tell them that? You should have been scheduled immediately. I’d also report it to the nhtsa.

Nichts

My service appointment for this issue is tomorrow. Will update with the diagnosis, etc. Vehicle has been fine in the meanwhile, just that damn orange light on the dash...

High Technology

You are very patient and I hope this is just simply a bad part (typically a sensor) -- while the manufacturing process is much better than it was over 20 years ago when we bought our first Benz, odd things still happen. We went through a few sensors in the first 10k miles (crankshaft position and I think camshaft position) and a transmission control module at about 20k miles on our '99 CLK. Since then we've owned an 2006 E500, a 2011 GL450, and currently own a 2009 SL550 and a 2020 GLC300, and have not experience similar issues with any of those cars.

I know your appointment is tomorrow, but if you ever end up in limp mode (or any other safety mode), drive (or call roadside to tow) the car to the dealer. Even if they can't get to it for a week, you deserve a loaner or a rental car, as a car that drops power output isn't safe to drive.

eddieo45

we had the CEL come on at about 1600 miles, no limp mode though. brought it in and they did a software upgrade. CEL came back though, and they swapped out a sensor.

Nichts

So I'm happy to report that my service department is fantastic in general. Very attentive and thorough advisors and techs. They diagnosed, tested and then test drove my GLC to see if they could see any faults, but none could be duplicated or displayed. The problem was a misfire on 1 and then on 4. They have attributed this simply to moisture in the fuel rail or poor quality gasoline (even if it was 93 and costs $6/gal!). So they reset and cleared the system and sent me on my merry way. There was no indication that the problem lay elsewhere.

During my 2 hr visit, two other brand new MBs came in for the exact same problem! This may be an issue in my area for some reason. Advisor also mentioned the highly sensitive nature of MB sensors and protective measures.

chassis

Thanks for the update. Hope it stays resolved. "Can't find the problem" and "bad gas" are standard non-answers from the MB service department.

Bad gas is blamed for problems with 1950s outboard boat motors and 21st century MBs.

Nichts

You'd think they'd tune out such deficiencies by now for the inconvenience it is to the owner, let alone for the quality control optics. I've owned Fords, Subarus, VWs, Mazdas, Hyundais, and not one of them ever had a misfire or a check engine light except the Mazda when the engine crapped out at 34k miles.

decorily

So you admit stuff happens!!

Nichts

The MB cost twice as much as the Mazda, so my expectations are of course higher.