SL/R231: Active Headlight Inoperable Error
Thread Starter
Newbie
Joined: May 2023
Posts: 8
Likes: 9
SL450
Active Headlight Inoperable Error
All, recently after washing my 2017 sl450, my turn signals started acting up. Inside the car, the indicator blinks rapidly, and the headlight and DRL on the passenger side isn't working.
Dashboard indicates to check right low beam, turn signal, etc.
I scanned the car and got the following,
E1n9 Left Headlamp (SG-SW-L)
N10/1 Front signal Acquisition and Actuation Module (Driver-side SAM)
The part number for the SAM says 212 901 48 07 but an internet search nets no results, save for some ebay listings.
Oddly, the left headlight is functioning correctly. It's the right one that is acting up.
Current symptoms are the passenger side headlight blinks continually, and the DRL and turn signals for that light are inoperable.
If anyone can offer some insight on this, I would appreciate it.
Thanks.
Dashboard indicates to check right low beam, turn signal, etc.
I scanned the car and got the following,
E1n9 Left Headlamp (SG-SW-L)
N10/1 Front signal Acquisition and Actuation Module (Driver-side SAM)
The part number for the SAM says 212 901 48 07 but an internet search nets no results, save for some ebay listings.
Oddly, the left headlight is functioning correctly. It's the right one that is acting up.
Current symptoms are the passenger side headlight blinks continually, and the DRL and turn signals for that light are inoperable.
If anyone can offer some insight on this, I would appreciate it.
Thanks.
Last edited by Malarkey; May 26, 2026 at 11:58 AM. Reason: updated info
Super Member
Joined: Jan 2019
Posts: 501
Likes: 166
From: Philadelphia area
2014 SL65 AMG, 2018 S560
All, recently after washing my 2017 sl450, my turn signals started acting up. Inside the car, the indicator blinks rapidly, and the headlight and DRL on the passenger side isn't working.
Dashboard indicates to check right low beam, turn signal, etc.
I scanned the car and got the following,
E1n9 Left Headlamp (SG-SW-L)
N10/1 Front signal Acquisition and Actuation Module (Driver-side SAM)
The part number for the SAM says 212 901 48 07 but an internet search nets no results, save for some ebay listings.
Oddly, the left headlight is functioning correctly. It's the right one that is acting up.
Current symptoms are the passenger side headlight blinks continually, and the DRL and turn signals for that light are inoperable.
If anyone can offer some insight on this, I would appreciate it.
Thanks.
Dashboard indicates to check right low beam, turn signal, etc.
I scanned the car and got the following,
E1n9 Left Headlamp (SG-SW-L)
N10/1 Front signal Acquisition and Actuation Module (Driver-side SAM)
The part number for the SAM says 212 901 48 07 but an internet search nets no results, save for some ebay listings.
Oddly, the left headlight is functioning correctly. It's the right one that is acting up.
Current symptoms are the passenger side headlight blinks continually, and the DRL and turn signals for that light are inoperable.
If anyone can offer some insight on this, I would appreciate it.
Thanks.
Unless this has been a long-standing problem odds are when the water finally dries out the problem will go away. The control module is located on the very bottom of the headlight so any water that gets in can affect it. There may be a crack or broken seal in the lens. If it happens often enough it will corrode the module connections, get into the module, and permanently damage it.
This is not unique to Mercedes. I know someone with a BMW having the very same problem.
Thread Starter
Newbie
Joined: May 2023
Posts: 8
Likes: 9
SL450
No specific codes that I could see but I can scan it again. I'm not very proficient with xentry though.
Prior to creating this thread, I did order the LED module for the passenger side headlight. Hopefully that is the "squeaky wheel" that needs some grease.
Thank you!
Prior to creating this thread, I did order the LED module for the passenger side headlight. Hopefully that is the "squeaky wheel" that needs some grease.
Thank you!
Super Member
Joined: Jan 2019
Posts: 501
Likes: 166
From: Philadelphia area
2014 SL65 AMG, 2018 S560
If you're using Xentry then there should have been a code number reported when doing a quick scan.
Super Member
Joined: Jan 2019
Posts: 501
Likes: 166
From: Philadelphia area
2014 SL65 AMG, 2018 S560
I take it that these are all under the "e2n9 right headlight" heading? Likely cause is the control module. There's two modules in each headlight. The control module sits at the bottom of the headlight and is susceptible to water damage. A replacement for that module has to be coded to the car.
To confirm the diagnosis the normal procedure is to swap the control modules between left and right headlights and see if the problem moves with the module. Unfortunately, it's a fairly labor-intensive process since the control module is not easily accessible. I'm dealing with this at the moment with the left headlight on my 2018 S560. In my case the base functions work on the headlight so it will pass inspection. I'll be swapping out the module in the next few weeks to see if I can regain the advanced features.
To confirm the diagnosis the normal procedure is to swap the control modules between left and right headlights and see if the problem moves with the module. Unfortunately, it's a fairly labor-intensive process since the control module is not easily accessible. I'm dealing with this at the moment with the left headlight on my 2018 S560. In my case the base functions work on the headlight so it will pass inspection. I'll be swapping out the module in the next few weeks to see if I can regain the advanced features.
Thread Starter
Newbie
Joined: May 2023
Posts: 8
Likes: 9
SL450
I have a new module, (231-906-76-00), I just haven't installed it yet. I was told it can be accessed from the fender liner, without removing the bumper cover, we'll see.
My headlights are working correctly and are no longer blinking, but the adaptive portion is still kaput. Very similar to your situation.
I'm not sure about the coding process once installed. I wonder if BenzNinja will still honor my subscription, now that he is no longer a forum sponsor. I hope so.
Anyway, thanks for your help. Cheers!
Last edited by Malarkey; Jun 2, 2026 at 08:08 PM.
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Super Member
Joined: Jan 2019
Posts: 501
Likes: 166
From: Philadelphia area
2014 SL65 AMG, 2018 S560
Correct!
I have a new module, (231-906-76-00), I just haven't installed it yet. I was told it can be accessed from the fender liner, without removing the bumper cover, we'll see.
My headlights are working correctly and are no longer blinking, but the adaptive portion is still kaput. Very similar to your situation.
I'm not sure about the coding process once installed. I wonder if BenzNinja will still honor my subscription, now that he is no longer a forum sponsor. I hope so.
Anyway, thanks for your help. Cheers!
I have a new module, (231-906-76-00), I just haven't installed it yet. I was told it can be accessed from the fender liner, without removing the bumper cover, we'll see.
My headlights are working correctly and are no longer blinking, but the adaptive portion is still kaput. Very similar to your situation.
I'm not sure about the coding process once installed. I wonder if BenzNinja will still honor my subscription, now that he is no longer a forum sponsor. I hope so.
Anyway, thanks for your help. Cheers!
In my case, I copied the contents of the existing module using DTS Monaco and then I transferred that to a used module I purchased using a bench setup. I have no idea whether it will work, but it should be educational.
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Junior Member
Joined: Nov 2023
Posts: 52
Likes: 16
2014 SL 550 R231; 2019 GLC 43 AMG X253 ; 2013 CLS 550 C218
I'm currently dealing with the same turn signal issue on the right (passenger side) headlight on my MY 2014 SL550.
I was able to remove the control module located under the headlight without taking off the front bumper. It sucks getting to all of the screws on the bottom of the module from removing the fender liner, but it can be done.
Make sure you have some torque wrenches shaped like an allen wrench with a short bend in the wrench. Getting a torque socket in there with a small 1/4" ratchet was near impossible for the back 2 screws.
I was unaware that this module had to be coded, so I'll be looking into this again as the replacement module did not correct my problem.
I was able to remove the control module located under the headlight without taking off the front bumper. It sucks getting to all of the screws on the bottom of the module from removing the fender liner, but it can be done.
Make sure you have some torque wrenches shaped like an allen wrench with a short bend in the wrench. Getting a torque socket in there with a small 1/4" ratchet was near impossible for the back 2 screws.
I was unaware that this module had to be coded, so I'll be looking into this again as the replacement module did not correct my problem.
Thread Starter
Newbie
Joined: May 2023
Posts: 8
Likes: 9
SL450
It sucks getting to all of the screws on the bottom of the module from removing the fender liner, but it can be done.
Make sure you have some torque wrenches shaped like an allen wrench with a short bend in the wrench. Getting a torque socket in there with a small 1/4" ratchet was near impossible for the back 2 screws.
I was unaware that this module had to be coded, so I'll be looking into this again as the replacement module did not correct my problem.
Make sure you have some torque wrenches shaped like an allen wrench with a short bend in the wrench. Getting a torque socket in there with a small 1/4" ratchet was near impossible for the back 2 screws.
I was unaware that this module had to be coded, so I'll be looking into this again as the replacement module did not correct my problem.
They will be coding the new units for me.
Newbie
Joined: Oct 2021
Posts: 7
Likes: 3
SL550
Headlight Issues
Sorry for your problem but this is a known issue. Some engineering genius at MB decided not to use sealed beams on SL headlights. Water can accumulate inside the headlight and it eventually finds its way into the electrical connection for the module. When I purchased my 2018 SL550 in 2020 I had major problems with entire system shutting down because of this issue. What can happen from this situation can be bizarre. Along with weird headlight and turn signal issues, the entire dashboard went blank, power brakes and steering not working, etc. After multiple dealer visits (car still under warranty) and some difficult conversations with the dealership, MB sent an "expert" in to fix the problem and it has not recurred since. I refused to take the car back until they could assure me the issue would not return but I really do not know exactly how they fixed the problems. Your problem might be helped by leaving the headlights on for long periods (creating heat to evaporate the moisture) and/or opening the rear of the headlight and inserting some desiccant to absorb moisture. I sincerely wish you the best of luck with this issue and wish I could provide details on a permanent fix.
Last edited by Jimbo2518; Jun 8, 2026 at 03:43 PM.
Super Member
Joined: Jan 2019
Posts: 501
Likes: 166
From: Philadelphia area
2014 SL65 AMG, 2018 S560
Sorry for your problem but this is a known issue. Some engineering genius at MB decided not to use sealed beams on SL headlights. Water can accumulate inside the headlight and it eventually finds its way into the electrical connection for the module. When I purchased my 2018 SL550 in 2020 I had major problems with entire system shutting down because of this issue. What can happen from this situation can be bizarre. Along with weird headlight and turn signal issues, the entire dashboard went blank, power brakes and steering not working, etc. After multiple dealer visits (car still under warranty) and some difficult conversations with the dealership, MB sent an "expert" in to fix the problem and it has not recurred since. I refused to take the car back until they could assure me the issue would not return but I really do not know exactly how they fixed the problems. Your problem might be helped by leaving the headlights on for long periods (creating heat to evaporate the moisture) and/or opening the rear of the headlight and inserting some desiccant to absorb moisture. I sincerely wish you the best of luck with this issue and wish I could provide details on a permanent fix.
Thread Starter
Newbie
Joined: May 2023
Posts: 8
Likes: 9
SL450
My headlights have decided to be fully functional again, on their own. I haven't replaced any parts yet.
I appreciate everyone's replies.
