Hello everyone,

I have a 2018 E300 4MATIC that is giving me these messages on the dash screen:

(Traction Control icon) Inoperative See Operator's Manual
Active Brake Assist Functions Limited See Operator's Manual




Last winter, these came on randomly but then went away by itself after it sit for a few hours and then nothing was heard of it again. Then this past week it has been coming on randomly again while I'm driving.

I noticed that the first few times it came on was when I was driving out of a small bump on a driveway, but this past week it started coming on more frequently without going over any bump. Whenever they are on, the car responds to gas pedal feedback much slower, like a 1-2 second delay whenever I came to a complete stop and go again. While driving, the car sometimes hesitates during cruise, like it suddenly slow down felt as if it lost power then immediately came back to normal.

And then today the CEL light came on today when this TC Inoperative and Active Brake Assist Limited errors was happening, just right before Thanksgiving
I brought it to an AutoZone to read the CEL and it doesn't seem to be anything serious regarding the CEL:
"Power Train System code P2138 - The values from the position sensors of the accelerator pedal are implausible relative to each other".




The CEL is a solid light (no flashing), and now stays on regardless of whether the TC Inoperative and Active Brake Assist Limited errors comes on or not. I was planning on driving 3 hours tomorrow to my mother for Thanksgiving, has anyone encountered a similar issue?

Believe it or not, this is not as uncommon as your think. Usually the problem is with adaptive headlights. Many have found that stopping the car, waiting and then turning the engine back on clears the messages.

Also suggest you do a thread search, as their are many on this subject.

Sorry it happens just before Thanksgiving and visiting your Mom.

Thanks for the tip. Hopefully it doesn't give trouble on the busy highways.

Yes, good point : stay out of the fast lane for a while. This can lead to limp mode without warning... actually this nagging is your warning.

This dangerous issue is caused by CAN-Bus crash of a few VIP modules.
Typically "domino effect" with ESP participating. One module upsets another.

Don't rush at getting many modules replaced without warranty of any results.

You should refer to local MB specialist or scan the chassis for fault codes with Amazon $150 Launch unit.

This issue benefit having good battery voltage which does not mean "more driving" as MB chassis in this condition "drain battery by driving".

Learn to religiously set IC to display voltage/amps while driving.

Stopping car safely in a parking when this happens helps clear/reset this transient issue well for a while.

> Free Workaround :
Driving with headlights switched ON guarantees ECU to request good alternator voltage so modules built with poor connections don't create transients.

You should confirm 14.4V with IC Display while driving.

So I drove 4 hours yesterday in what was supposed to be only a 3 hours trip because I set my Google Maps to avoid highways.

When I initially started driving, right when I just got out of my complex the TC Inoperative + Active Brake Assist Limited msg came on again accompanied by the usual, very brief sudden loss of power. I stopped by a gas station to fill up, it went away. Drove it for 5 minutes, came on again after I went over a very small but noticeable bump along with the Check Engine Light. I stopped and parked the car in an empty parking lot for about 2 minutes, turned back on, CEL still there but no TC Inoperative + Active Brake Assist Limited. Put in reverse and just as I started reversing out both those msg came back on, so I parked back in and waited another 5 minutes.

This time all lights are off, no problem. I went out and started warily driving and to my surprise, no more CEL or TC Inoperative/Active Brake Assist Limited msgs for the rest of the 4 hours drive.

Here's fingers crossed for the return trip. I have a diagnosis appointment with a local MB dealer on Monday, hopefully it's just a small issue like a loose cable or dirtied sensor.

I posted an update but for some reason it says it needs moderator approval... been 2 days so I guess I'll post again.

So on Thanksgiving I decided to go anyway. At first when I started the car, the CEL was gone, and then the same error messages also came up just 5 minutes after I started driving and went over a small bump on the road. I stopped by for gas, it disappeared after I restarted. Drove for 3 minutes it came back on, parked it inside an empty parking lot for a few minutes, restarted, came back on right when I'm pulling out... I pulled back in and let it sit for 5 more minutes then restarted. No more errors.

I chose 'Avoid highways' in the route options on Google map just to be safe, what is supposed to be 3 hours turned into 4. Drove the rest of the 4 hours with not a single issue came up, no CEL, no error messages. Very odd. But hey, I saved tons of gas and the drive was much more relaxed rather than using the highway, as I'd just found out. Went through a bunch of small towns I'd never heard of and the road coupled with Thanksgiving was sparse, very enjoyable drive.

On the drive back home, error messages came up again after a few minutes of driving. Stopped by for a haircut on the way, all msgs gone after I started the car again and then drove the rest of the 4 hours home with no further issue again. It did came back up a about 10-20 minutes after I started driving from the haircut place, but I restarted it on a red light and all was good for the rest of the drive.

Very odd, hopefully just a small issue. Has an appointment at a local MB dealer for next Monday for a diagnosis.

I also just realized that the 'hesitation' I mentioned when the TC and Active Brake Assist error msgs were on was most likely the Active Brake Assist acting up, because it felt similar to how when one drop a gear and do an engine brake (albeit a bit less extreme). I also connected the dots to when my car's parking sensors would randomly beep really hard randomly at times with the 360 screen on monitor and red borders as if something was close even when nothing was close to me, so maybe dirty if not faulty sensors.

Glad this trip ended up safe and fun.
Radars and parking sensors are very qualified to cause chaos including a "No Crank, No Start". Glad you did not get stuck.

Local MB specialist will get this all sorted out for ya in one shot.

Be prepared to help them reproduce the conditions that causes your issue.
Happy Holiday.

I know many MB owners who don't keep their wheels clean. This can cause errors with the speed sensor as it gets all dirty and can't read and then throws and error.

I would take off the wheels and clean the everything including the knuckle. Traction is part of the speed sensor and so is the braking but if you have a module reader, you will see the errors inside the module and figure out exactly what is causing the error.

My 2018 E300 got same issues, I have done a lot of research and troubleshooting. Finally I found that the recall letter I received on October 4, 2024 is talking about this issue. the letter title is warranty extension: electrical wiring and plug connection on the accelerator pedal. The wire harness connected to the accelerator pedal is defected. I actually removed the pedal and found the wire harness was pinched or jammed between the pedal base and the floor metal. There is a hole for the harness routing but not used. It will be 10 years warranty now. I have booked a repair service. Hope it will fix this problem.