Hi guys, I own a 2020 x167 GLS450 for a while, and in the past year, I faced 2 identical failures during my drive.
The 1st accident happened last autumn, I was driving on a country road, a nice pavement road, and suddenly, the 48v warning light was on (YELLOW) and then the Coolant Too Hot warning light (RED) was on, and the car lost its power. 1 minute later, the 48v warning light (RED) was on. I parked on the side of the road, turned the engine off, I checked the coolant level and temperature, and both were pretty normal. Then I checked the 48v status through the car and it remained 79% of power. Since nothing looked wrong, after waiting 5 minutes, I turned it on, the check engine light (YELLOW) was still on, but the power was back, and the car just drove like normal. So I drove it to my office, and interestingly the check engine light was off in the evening. I took the car to Mercedes dealer and they didn't find anything wrong either. They told me they updated the 48v software and it seemed like could resolve the issue.

And I faced 2nd accident today and it was similar to the 1st one. I was driving on i95 and the 48 warning light was on (YELLOW) and several seconds left the Coolant Too Hot warning light (RED) was on again, and also it lost power. Based on the previous experience, I parked the car and checked everything was good, nothing abnormal. I turned it off and turned it on again, and the power was back and the car behaved like normal. Since this accident just happened, the check engine light (YELLOW) was still on, but I think it might disappear in tomorrow.

These 2 failures are too identical, I think they have the same root cause, and Mercedes didn't fix it in the last time. I checked the Coolant level, Coolant temperature, 48v power level, 12v power level, and nothing wrong among them, I guess this issue might caused by a loose contact? but I am not sure, and I haven't gone to Mercedes workshop yet. Do you have any thoughts or suggestions?

PS: I was trying to find some common usage before I faced those 2 failures. The 1st one happened on a foggy day, and I drove it on a wet non pavement road a day before. And the 2nd one just happened after I went to an automatic car wash. Maybe water causes this error? But interestingly, the car works great during rainy days or snow days... And it makes me really confused....

 

I wonder if your 48v coolant pump is intermittent.
Or maybe the turbo cooler.

Good job at describing the surrounding events. Maybe pics for the Service Department.
Good luck with this.

 

My car had a 48v recall last Dec. I heard they updated the software on the 48v. Then the exact thing that happened to you also happened twice to me, and I was also driving on i95, and my dealership did the same thing and found nothing...

 

Thanks for your suggestion! I will let the service department know, and hopefully they could find the real issue.

 

that is too bad for a car like this... So far my car is under warranty, but I am afraid if this issue goes crazy after the warranty, and the price to fix if I need to pay for it... If Mercedes cannot find the root cause and this issue is replicable during this year, I would consider trading this car for other brands....

 

Hi--Did you get an solution to your warning light situation. I'm having a similar problem with my CLS450. Coolant warning light, then check engine light. Car goes into 'limp' mode. But coolant is fine. Did the recall software update--but did not fix.

 

so far my car is good, I might have experienced 2 times of recalls, to update the 48v software. And frankly, the car performed perfectly, no light went on for this one and half year after the software update. I recommend you shut down the car for 2-3 hours, if the light goes off, then nothing big deal. The software update just to eliminate false positive alerts.

 

All my alerts have been false. Just got the sw update on Wednesday--but got coolant light warning and 'limp mode' on the way home. Had car towed back to dealer. At this point dealer is still looking for problem.

 

ohh... thats too bad, I hope they will cover the cost..

 

Did you ever get an update on this? Having identical issue.

 

My problems turned out to be the cooling fan chafed the coolant pump cable. Even more strange is that MBZ had a recall on this problem but only for the 2019 CLS450. Mine is an early 2020--but had the same problem. I need to contact the NTSB about this---if maybe MBZ did not. --- Anyway, the fix was to re-route the cabling away from the cooling fan. The dealer paid for repairs. The car works great now.