M-Class (W166) Produced 2012-2015

2012 ML350 Turn Signals not working

Old Apr 24, 2017 | 10:56 AM
  #1  
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ML350
Exclamation 2012 ML350 Turn Signals not working

On longer road trips the turn signals on my 2012 ML350 stop working. The emergency flashers still work. After stopping and restarting the engine, the flashers will work again, for a while, then the problem repeats, over and over.
The first time it will occur is after about 70-80 miles, when starting from cold. Then the intevals become shorter, like every 20-30 miles.
This is not only frustrating, but outright dangerous.

HELP!!!
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Old Apr 24, 2017 | 10:57 AM
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bone stock E55 AMG
moved to W166 forum...
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Old Jun 5, 2017 | 09:41 AM
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2012 ml 350
Ml 350 2012 turn signal out

Hi
Did you found where the problem come from?
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Old Jun 5, 2017 | 01:39 PM
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2020 GLE350 2020 Toyota Rav4H AWD XLE
blown fuse most likely, are you still under warranty?
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Old Jun 5, 2017 | 06:42 PM
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2009 e class 2012 ml350
Originally Posted by Pitbaron
On longer road trips the turn signals on my 2012 ML350 stop working. The emergency flashers still work. After stopping and restarting the engine, the flashers will work again, for a while, then the problem repeats, over and over.
The first time it will occur is after about 70-80 miles, when starting from cold. Then the intevals become shorter, like every 20-30 miles.
This is not only frustrating, but outright dangerous.

HELP!!!
you might need a steering column module, common problem, had mine replaced for the same problem
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Old Aug 11, 2018 | 12:39 PM
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2012 ML_250CDI_4MATIC (W166)
I do have the same problem with my 2012's W166 (250CDI), and wanted to know if the root cause of this issue has been found ?
what was the fix ?
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Old Aug 12, 2018 | 12:00 PM
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Originally Posted by xxl121
I do have the same problem with my 2012's W166 (250CDI), and wanted to know if the root cause of this issue has been found ?
what was the fix ?
I still have not identified the real cause, still have not fixed it yet. Went to an MB dealer but they cannot find anything definite either. It definitely has to do with the steering column switch, as now I occasionally also find issues when operating the left or right turning signal. When operating the switch, the turn signal will work (blink) 3 times, then stop, same as if I just bump it, even though it is still locked in. If I just slightly touch the turn signal again, it will keep operating normal.
Now, the MB dealer tells me that they want to keep the car and play with it for a while to see if they can fix it. I am hesitant, because I am afraid that in the end I will pay for their time trying to fix it and then still have to replace the module.
I will just bite the bullet and order a new switch module and have it replaced.
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Old Aug 12, 2018 | 12:07 PM
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Sir, you are clearly low on blinker fluid

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Old Sep 17, 2018 | 06:13 AM
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From: Tunisia
2012 ML_250CDI_4MATIC (W166)
I have taken my car (ML-250) to the dealer and had a full system scan done by Xentry, below the error code (in french).
it is a common problem apparently and I will have to change the combination switch ... repair work not done yet, as part not available from the local dealer. (part cost ~500 USD in Tunisia - might be different in your country)


XENTRY report
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Old Oct 5, 2018 | 01:55 PM
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Problem was diagnosed as a problem with the multi-function Switch, was replaced today. $795 with parts and labor.
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Old Oct 5, 2018 | 09:06 PM
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Originally Posted by Pitbaron
Problem was diagnosed as a problem with the multi-function Switch, was replaced today. $795 with parts and labor.

So it turned out to be $35.00 part. Ha ha
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Old Oct 28, 2018 | 09:20 AM
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2012 ML_250CDI_4MATIC (W166)
Pictures of the replaced defective part


Rear view of defective part

Front view of defective par
I thought interesting sharing pictures of the part to be replaced. Part number is also visible.

Last edited by xxl121; Oct 28, 2018 at 09:22 AM.
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Old Dec 5, 2018 | 09:29 AM
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Any update from MBUSA? Maybe a TSB.
Anyone have a part number or does it have to be the whole steering column?
It's been a problem with our family's W166.
I think this is a safety hazard. Don't wanna get pulled over for switching lanes without signaling, or worse cause an accident.
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Old Jan 28, 2019 | 02:35 PM
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Our GL550 just had the B178F00 error, I'm going to see if it can be cleaned/repaired, probably just a problem with poor electrical contact.
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Old Jul 7, 2020 | 03:47 PM
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Mercedes ML 250 Blue Tech 2012
2012 ML 250 Turn Signals not working

Originally Posted by Pitbaron
On longer road trips the turn signals on my 2012 ML350 stop working. The emergency flashers still work. After stopping and restarting the engine, the flashers will work again, for a while, then the problem repeats, over and over.
The first time it will occur is after about 70-80 miles, when starting from cold. Then the intevals become shorter, like every 20-30 miles.
This is not only frustrating, but outright dangerous.

HELP!!!
a good compromise solution which will cost you nothing is to only slightly touch the indicator lever so as to only just activate the indicator, but not actually switching it on. Keep you finger on just long enough till not needed. It then seems to keep on working!
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Old Dec 15, 2020 | 01:06 PM
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Mercedes ML 350 W166
Auxiliary battery replaced

I had the same problem. It was also worse on hot days. About a year after it started I still had not solved the problem, but then my auxiliary battery light came on. I got the auxiliary battery replaced for about A$500 and now my indicator works properly!
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Old Dec 16, 2020 | 11:06 AM
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Too many german broads
Originally Posted by amartuccio
I had the same problem. It was also worse on hot days. About a year after it started I still had not solved the problem, but then my auxiliary battery light came on. I got the auxiliary battery replaced for about A$500 and now my indicator works properly!
$500 for an aux battery sounds like robbery
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Old Dec 22, 2020 | 11:14 PM
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Turn Single not working but rests. 2012 ML350

Seems like this should be a safety recall. The turn signals just stop working on a long drive. Both sides go out but the emergency flashers still work. Shutting off the car seem to reset them and they will work normally for a while.
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Old Dec 23, 2020 | 09:14 AM
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I agree. Definitely a safety issue.
Yet another fine example of modern German engineering. The bean-counters higher up have ruined the brand.
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Old Dec 23, 2020 | 09:44 AM
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I called MBUSA and filled a complaint when we had a 166. If enough of us do that, they'll do something about it.
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Old Feb 21, 2021 | 01:24 AM
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W166 BlueTEC Porsche 911SC
My 2012 BlueTEC have the same issue 6 months ago and replaced the unit.
But, the issue cames back today. Suddenly, both left and right signal doesn't work. I turned off the car for around 15 minutes but the issue still there. Than, I drove five minutes to another place and stop for around half an hour. It works normally. I did noticed the message about blind spot assistant not working properly.
I do believe there is an issue on the ECU. It needs the reset.
Moreover, I have intermediate rough idle issue. I am driving city all the time. It happens when the idle goes upto around 700rpm.
​​​​​
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Old Mar 25, 2021 | 04:02 PM
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2012 ML350 Diesel
Turn/blind spot not working

Originally Posted by Roger126
My 2012 BlueTEC have the same issue 6 months ago and replaced the unit.
But, the issue cames back today. Suddenly, both left and right signal doesn't work. I turned off the car for around 15 minutes but the issue still there. Than, I drove five minutes to another place and stop for around half an hour. It works normally. I did noticed the message about blind spot assistant not working properly.
I do believe there is an issue on the ECU. It needs the reset.
Moreover, I have intermediate rough idle issue. I am driving city all the time. It happens when the idle goes upto around 700rpm.
​​​​​
I have just experienced exactly the same issue, did you find the problem and a solution; don't want to get a bill from Mercedes for more than the cars worth to find it's a fuse or such.
Regards Dave.
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Old Mar 25, 2021 | 04:07 PM
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Originally Posted by Dpick
I have just experienced exactly the same issue, did you find the problem and a solution; don't want to get a bill from Mercedes for more than the cars worth to find it's a fuse or such.
Regards Dave.
I have a thread on how to replace the unit.
https://mbworld.org/forums/gl-class-...acting-up.html
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Old Mar 30, 2021 | 01:15 AM
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W166 BlueTEC Porsche 911SC
Originally Posted by Dpick
I have just experienced exactly the same issue, did you find the problem and a solution; don't want to get a bill from Mercedes for more than the cars worth to find it's a fuse or such.
Regards Dave.
I did rest right after my post. Up to today, it works without any problem. Here is the YouTube link
.

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