Active Brake Assist traction control inoperative error update

[JustmeJB]

Picked my new to me 2017 e class estate up around a month back and fairly soon after I got the active brake assist and traction control malfunction errors along with the EML light lit up. Got a years warranty with it so booked it in at my local indy (2 week wait). Dropped the car off yesterday and the diag states new Nox sensor and new throttle pedal.
I was expecting the speed/ABS sensor issue which is well documented on here so this was a surprise. Not particularly concerned as it at least replace two components one of which is known to fail anyway and the warranty company agreed no problem for the £1k or so worth of parts plus labour.

Has anyone else experienced these issues combined? At this stage I'm fully expecting the warning lights to return shortly after the repairs. Cars booked in for a weeks time so will update once I've been for a decent drive.

 

[JustmeJB]

Ok so an update. I got the car back yesterday after the NOX sensor 2 and the throttle pedal were replaced. Gave the car a run out this morning and just as I was about to head home the brake assist inoperative message flashed up again along with the EML. Drove to the indy whilst the message was still there and luckily enough he had time to plug the car in. Diagnosed the throttle pedal again. Apparently the readings are all over the place when the pedal is pressed so it's booked back in. Really hoping this can be solved and I haven't bought a Friday night car.
Having read posts on this forum I do still wonder if it's the speed sensor but I guess it doesn't harm to have everything else looked into and changed where needed.

 

[markjay]

Does the Indie have STAR?

 

[JustmeJB]

Not sure actually. I'll find a way to check/ask him.

Would the use of that diagnose the errors differently?

 

[JustmeJB]

So the saga continues. I took it back to the indy and he again diagnosed the throttle pedal so dropped it off for that and he mentioned they had reset everything and calibrated and it seemed to have calibrated differently this time so he felt sure it was fixed. Drove out and just as I was feeling confident the errors returned. Initially called the indy but then called the dealer I collected it from and he agreed to pay the difference in what the warranty will cover and what a main dealer charges. Dropped it in to the main dealer and they did a software update and asked me to monitor it. Sure enough on my way home the errors returned so drove straight back to the main dealer to show them the errors and they advised to book it in for a full check involving removing the front bumper (3 hour job allegedly!!!). So they now have the car over the weekend and beyond if needed to get to the bottom of the issues. Fingers crossed they sort it otherwise I fear I will need to return it (goods not fit for purpose) to the dealer I got it from. Hope not as when the errors are not there it's a really nice car to drive.

 

[JustmeJB]

Ok so hopefully the last update for this issue. Dropped the car off at the main dealer and they diagnosed the wiring loom to the throttle pedal. So about 50 quids worth of parts and a lot more in labour but should now be all ok. Early indications are good so fingers crossed that's the end of it.
I originally suspected a wheel speed sensor and suggested that to the main dealer but the indicator that that wasn't the issue was the EML along with the brake assist and traction control errors. If it was the speed sensor the EML wouldn't be lit.

 

[geoffus]

Hope it’s sorted, mine had the EML, ABS and traction control come on when I had a front wheel sensor fault. Also the steering became very heavy as if guiding you to drive slow.

 

[tonysmb]

I had a discussion about this sort of thing with an MB technician and there was a thought that if the traction control is the type that works by cutting engine power then that might well trigger the EML, likewise if the car has speed variable electric power steering, the ecu is unable to determine vehicle speed, hence affects the steering.

All this stuff is great when its working but so much is now interlinked that one sensor fault can be enough for the car to throw a tantrum.

 

[JustmeJB]

Hope it’s sorted, mine had the EML, ABS and traction control come on when I had a front wheel sensor fault. Also the steering became very heavy as if guiding you to drive slow.
View attachment 146006

My steering would randomly go heavy too. I would also lose cruise control, the parking brake wouldn't work, auto start stop wouldn't work and the engine would idle at around 800 rpm with the brake pedal depressed and would then rise to around 1200 revs when the brake pedal was released. Made for interesting times when at traffic lights or reversing into tight spots. All this would be random too. Sometimes I could start the car and there would be no dash lights at all and then around 20 minutes of driving and the errors and EML would appear with some or all of the above symptoms. Stop the car briefly and they could disappear or stay on. Frustrating but I got used to them being on it was kind of a treat when they disappeared lol.

 

[JustmeJB]

I had a discussion about this sort of thing with an MB technician and there was a thought that if the traction control is the type that works by cutting engine power then that might well trigger the EML, likewise if the car has speed variable electric power steering, the ecu is unable to determine vehicle speed, hence affects the steering.

All this stuff is great when its working but so much is now interlinked that one sensor fault can be enough for the car to throw a tantrum.

Agreed all good stuff when working but the slightest deviation seems to throw an error. I very briefly owned a nearly new Nissan Navara and the EML came on driving home from the dealership after I picked it up. Called the sales guy and he asked if it had run low on fuel which it had. He told me to fill it up and run it over a few days to see if it went out (which it didn't - long story and multiple other faults which resulted in me returning the car for a full refund). I thought his suggestion was BS until I read the manual and lo and behold it mentions if the filler cap isn't placed on correctly it can trigger one of the euro 6 sensors and throw the EML. So glad I got rid of that.

 

[WilliamParsons]

I had a discussion about this sort of thing with an MB technician and there was a thought that if the traction control is the type that works by cutting engine power then that might well trigger the EML, likewise if the car has speed variable electric power steering, the ecu is unable to determine vehicle speed, hence affects the steering.

All this stuff is great when its working but so much is now interlinked that one sensor fault can be enough for the car to throw a tantrum.

The input and interactions between various vehicle systems, such as traction control, engine management, and electric power steering, can indeed influence one another, and in some situations, they might trigger warning lights or affect the overall vehicle performance. Here are some insights into how these systems can be interrelated:

 

[JustmeJB]

OK so hopefully a final update on this issue and a bit of good news which always seems to be forgotten on forums sometimes. We had a round trip of nearly 500 miles over the weekend with no errors or issues after the wiring to the throttle pedal was replaced by the Mercedes main dealer so touch wood it's all sorted now. Very happy with that and the car is lovely to drive again.

 

[Smiley]

Good that you have found the root cause of the problem and had it fixed - and that you take the time to come back to the forum.
It does beg the question of how a passive component (the "wiring") fails on a six yr old car.

 

[WilliamParsons]

Good that you have found the root cause of the problem and had it fixed - and that you take the time to come back to the forum.
It does beg the question of how a passive component (the "wiring") fails on a six yr old car.

It's not uncommon for wiring or electrical components to fail in vehicles, even on relatively young cars. Factors like wear and tear, exposure to harsh conditions, manufacturing defects, or even rodents can lead to electrical issues over time. Regular maintenance and prompt diagnosis and repair can help address these problems as they arise.

 

[geoffus]

Good that you have found the root cause of the problem and had it fixed - and that you take the time to come back to the forum.
It does beg the question of how a passive component (the "wiring") fails on a six yr old car.

I agree, how do you wear out wiring the wiring of a throttle pedal, unless it was a manufacturing fault, I wonder if they showed you the faulty wiring after replacement.

 

[JustmeJB]

I agree, how do you wear out wiring the wiring of a throttle pedal, unless it was a manufacturing fault, I wonder if they showed you the faulty wiring after replacement.

Sadly I didn't ask to see the old wiring so I don't know the root cause. I do however know that it had been worked on previously. Twice by my local indy and I suspect by whatever garage the previous owner used. So it could be that multiple attempts weakened the wiring maybe due to hamfistedness. When my main dealer carried out the repair one of the items changed was a connector so that may explain some of it.
It may be that the errors and warning lights played a part in the previous owner changing it for something else due to either money already spent or the threat of a large bill for diagnostic and subsequent repair. If that is the case it's worked out well for me as the car is very nice and this issue has been resolved under warranty and a payment in kind from the dealer I bought her from for the wiring as that's not covered under the warranty.

 

[JustmeJB]

It's not uncommon for wiring or electrical components to fail in vehicles, even on relatively young cars. Factors like wear and tear, exposure to harsh conditions, manufacturing defects, or even rodents can lead to electrical issues over time. Regular maintenance and prompt diagnosis and repair can help address these problems as they arise.

True, I've very nearly fallen foul of mice having a go at one of my motorcycle wiring looms. They had stareted to build a nest in the airbox too having knawed through the foam airtube surround to get in. Luckily spotted the droppings and placed many traps around the garage after that. Lucky escape for sure.
For this issue it may be that the routing of the wiring was close to a moving object and over time it chaffed away, or as above it was weakened from multiple attempts to repair.

 

[Smiley]

It's not uncommon for wiring or electrical components to fail in vehicles, even on relatively young cars. Factors like wear and tear, exposure to harsh conditions, manufacturing defects, or even rodents can lead to electrical issues over time. Regular maintenance and prompt diagnosis and repair can help address these problems as they arise.

I would not agree. It is uncommon for wiring to fail - ime it only fails if it has been poorly designed eg not enough heat protection if in the engine bay or rodents have got at it. Not much that regular maintenance can do about that. It is more about taking precautions against the rodents in the first place.

 

[JustmeJB]

I would not agree. It is uncommon for wiring to fail - ime it only fails if it has been poorly designed eg not enough heat protection if in the engine bay or rodents have got at it. Not much that regular maintenance can do about that. It is more about taking precautions against the rodents in the first place.

I guess it depends on the the function of the wiring. A previous bike I owned (Suzuki TL1000S) was renowned for cooking the starter relay connector which would leave you stranded wherever it decided to cook itself. The mod was upgraded wiring (and new connectors obviously).

Apparently some wiring in the boot of some Mercedes is close to the hinges so is susceptible to rubbing the sheath away and causing issues.

I agree wiring shouldn't be the weak link given it's job but there's factors in play that can mean it ends up the weak link.