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Hello MBWorld: I'm having an issue with the Blind Spot Indicator (BSI ) on right side that seems to be stumping my usual mechanic as well as MB Dealership. Here are the details.
1. Problem began just after Xmas when I hit a large pothole on rear passenger side. Next day the right BSI began malfunctioning. Brought to shop and they replaced the R/R BSI and cable harness. Problem persisted.
2. After 10,000 kms I have narrowed down some of the symptoms that accompany when the BSI malfunctions.
A. Only malfunctions when the right turn signal is activated. During this time the BSI will give faulty readings and/or stay RED on the external mirror. Then it will take awhile to reset. Either by slowing to a stop, therefore resetting the logic, or on the hwy for a long time it will self-reset or by manual disable/enable of the BSI system it will finally begin operating properly.
B. Recently MB dealership went and replaced both BSI units and the wiring harness. Mechanic drove it back to his shop without malfunction. Over the weekend it resumed same issues.
C. Went back to the mechanic. He put the computer on it. No errors. While driving back home it worked flawlessly.
D. Conclusions: Something other than the BSI units and the wiring harness. Checked fuses to make sure they were well seated. They were. Now suspecting maybe a fault or intermittent connection with external mirror or even cortesy lights as they all seem to be on the same fuses, 2 & 3.
Trouble finding any literature that connects the external mirror with turn signal with BSI system.
Any suggestions ?
W212 2011 E350 4matic Estate Wagon.
Last edited by Wayner; Apr 17, 2019 at 01:22 PM.
Reason: Grammer
Hello MBWorld: I'm having an issue with the Blind Spot Indicator (BSI ) on right side that seems to be stumping my usual mechanic as well as MB Dealership. Here are the details.
1. Problem began just after Xmas when I hit a large pothole on rear passenger side. Next day the right BSI began malfunctioning. Brought to shop and they replaced the R/R BSI and cable harness. Problem persisted.
2. After 10,000 kms I have narrowed down some of the symptoms that accompany when the BSI malfunctions.
A. Only malfunctions when the right turn signal is activated. During this time the BSI will give faulty readings and/or stay RED on the external mirror. Then it will take awhile to reset. Either by slowing to a stop, therefore resetting the logic, or on the hwy for a long time it will self-reset or by manual disable/enable of the BSI system it will finally begin operating properly.
B. Recently MB dealership went and replaced both BSI units and the wiring harness. Mechanic drove it back to his shop without malfunction. Over the weekend it resumed same issues.
C. Went back to the mechanic. He put the computer on it. No errors. While driving back home it worked flawlessly.
D. Conclusions: Something other than the BSI units and the wiring harness. Checked fuses to make sure they were well seated. They were. Now suspecting maybe a fault or intermittent connection with external mirror or even cortesy lights as they all seem to be on the same fuses, 2 & 3.
Trouble finding any literature that connects the external mirror with turn signal with BSI system.
Any suggestions ?
W212 2011 E350 4matic Estate Wagon.
As the blind spot sensors are radar sensors by my understanding I would check the sensor installation myself to make sure it is in place correctly and not moving.
Only major components in rear are left & right radar sensors (500 in diagram) + wiring harness (390). Should have checked if software is current, was this confirmed.
Hello Konigstiger: Thanks for the part description and BSI operation picture.
On my trip down to California and back, many sections of road were in complete isolation of any sort of RF interference, phone service, guardrails, etc., and problem still persisted. So I think we can rule out RF interference and structures.
When they told me the wiring harness had been replaced I was picturing, in my mind, something completely different. So this pic has enlightened me on that point.
As I have an appointment with them again soon, I will ask them about the computer software.
I'm still hoping to pursue other ideas prior to that time.
I have also been searching for videos describing the DIY technique of accessing these modules and investigating for myself, as suggested by Arrie, but not much out there that I have found so far.
Hello Konigstiger: Thanks for the part description and BSI operation picture.
On my trip down to California and back, many sections of road were in complete isolation of any sort of RF interference, phone service, guardrails, etc., and problem still persisted. So I think we can rule out RF interference and structures.
When they told me the wiring harness had been replaced I was picturing, in my mind, something completely different. So this pic has enlightened me on that point.
As I have an appointment with them again soon, I will ask them about the computer software.
I'm still hoping to pursue other ideas prior to that time.
I have also been searching for videos describing the DIY technique of accessing these modules and investigating for myself, as suggested by Arrie, but not much out there that I have found so far.
Regards, Wayner
You said the problem started when you hit a hole or something. Hitting a hole on road does not change your software code on any computer module. It can change the physical attitude of a mechanical component, like the radar sensor.
How do do you know your sensor was really changed other than you were told so?
This is why is said to check the sensor mounting yourself. I don’t know how to get to the sensors in the back. Is it thru the trunk or do you remove tire well coverings but in any case it should not be too hard.
1. Wrt the software, yes I understand your point and I think Konigstiger has explained that already as I also understood what he was saying.
2. In a word.... TRUST. I've known personally, my mechanic for over 30 years, and in no way would a reputable MB dealership even try and scam the customer with false information. In this day and age of social media it would be a death sentence to them if they were ever caught doing something like that.
3. I would still like to figure out how to DIY on this issue, but am hesitant until I see a procedure to assist me. Until then I will rely on the certified mechanics. But as this particular problem has eluded them I decided to reach out to the MB community incase they have experienced something similar.
I've had this error come up on my '12 w212. Initially, I just disabled the BSI because I don't really care. That turned off the warning as it was just off. When this happened I got under the car cleaned the inner bumper because I'd read about debris or dirt causing issues. I found one bracket loose so glued that. Connections were tight and there was no visually apparent issue, no surprise there.
However, now I am randomly getting the warning and amber lights in the mirrors. As I don't care about the function I'm just trying to get it to stop reminding me there is a fault. I'm wondering what might cause this. Perhaps get under the car and unplug the sensors? Thoughts? Any ideas? I think I read about a fuse, maybe check that? I just want it to stop popping up. Either work or don't!
Hello Jimh6 and everyone else who was kind enough to offer advise.
I brought the car back into the MB Dealership shop a couple days ago. The head mechanic took the car for a ride to re-confirm that the problem still existed.
I watched & waited for him to return, to have a chat with him. I described how the problem all began and when he heard that he had a better idea of what to look for. Sure enough it was a loose sensor mount on the right side. They applied epoxy to the mounting bracket and it has worked flawlessly since then.
So, Jimh6, you may want to look at those mounting brackets again. Another thing I found out was that the location of these sensors was a poor design and water will collect and corrode the contacts. A couple years ago, when the car was still under warranty, I think it was the left one, they replaced the sensor but also drilled holes into the underside of the bumper to allow for better drainage.
Why the loose mount interfered with the turn signal I have no idea and none were brought fwd. At least next time I'll have a better idea on how to troubleshoot the problem. Hope some of this info helps you and others, Good Luck.
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