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2011 S550 RWD
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Discussion Starter #1 (Edited)
I have been getting the blind spot assist inoperative error for the past 1 week.

When I start the car, everything is good. But like clockwork, at precisely 5 min after startup, it throws that error, along with the Pre-Safe error. After that it randomly resolves itself and goes out again. I am guessing there is some loose connection somewhere. BTW, it started soon after the outside temp here in NJ has been dropping. Wonder if it's related to that.

I did some research but have not found anything conclusive as far as how to diagnose it or fix it for that matter. Besides taking it to the dealer or using a custom scanner which I don't have.

Where is the blind spot assist sensor located? Is it inside the rear bumper? What are those small dots on the bumper? Are they blind spot assist sensor or parking sensor?

Any tips suggestions on how to proceed would be appreciated.

Thanks!
 

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2011 S350 Bluetec
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I've just started getting this recently. It seems to have started after I went away for three weeks and the car sat in an airport car park unused. On return the battery seemed to struggle to start the car but has been okay since.

I think that sometimes on cold mornings I get the errors but after I've driven for a bit the warning disappears and the yellow LEDs in the mirrors go out which I've been assuming means that the battery has more charge in it.
 

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I have a 2014 GLK 250 and my vehicle has developed the same problem. Ironically my problem also began after have had the car parked for three weeks too. Don't know if that's related or coincidental, but I thought I would mention that. I have not yet fixed the problem, but I have been trying to research the cause. So far from what I've found, the problem is likely a bad blind spot sensor. The sensor uses radar to detect objects. It sends out a radar signal and measures the time it take to get a reflection signal from some object. I uses that to calculate how far an object is away from the sensor. The part is commonly referred to as a blind spot detector, blind spot radar, object detector or location detector.

I've read that the part can commonly fail do to rainy weather or cold temperature. On my vehicle, the sensor is located below on the passenger side rear bumper. (Not physically the bumper, but the side panel in that area). The part is easily accessible (lying on your back under the vehicle) without having to take anything else off or the need to jack up the vehicle) For my vehicle, the dealer price for the part is $695, but you can get a new OEM part for around $560 and an aftermarket one for $365. On ebay, you can get a used one for around $150 - $200. I'm leery, about getting a used one or using an aftermarket one.

The part is contained in a holder that has a clip that holds it in place. It's a bit confusing on how you go about taking the clip off. I got mine off by using a small flat head screw driver and gingerly prying it out. Be careful, you don't want to break the plastic clip or holder. (That small plastic clip around $30, and the holder is even more.) The next problem you'll run into is disconnecting the electrical connection. From the bottom side of the connector that you can reach when the sensor is in place, their is a shim piece that you need to take out before you'll be able to disconnect the wiring. I used that same little flat head screw driver to push it out. (Again, be ginger in getting it out). Here's some pictures so you can see what you're dealing with.
BlindSpotDetector.jpg
BlindSpotHolder.jpg


What I'm currently trying is to make sure the part is internally dry. I've read that the part can disfunction if it gets wet. I have it place by a furnace register. The part is fairly well sealed and protected from water but I was able to blow some air though the casing and the bottom sealed cover, so I can't rule out the possibility that water didn't get inside. I've also read that it can be problematic if the part gets dirty.

There's also some confusion as to whether the sensors on the front and back bumper may be the culprit. From what I've read, most of those sensors are related to parking assist and not blind spot assist. My parking assist sensors seem to be working fine even with the blind spot detector removed. When reading online about this problem, those things seem to get mixed in with the discussion, but they're really independent circuits. I've also read that on some Mercedes, that the bind spot detector circuit sometimes blows a fuse and its tied to the same circuit that the windshield wiper is connected to. In my case, my windshield wipers are working fine. The fuse box diagram that I found online for my vehicle doesn't say for sure what circuit the blind spot detector is connected to and I don't have a wiring diagram.

So from everything I've read, it so far looks like my blind spot detector has gone bad. I'll wait a couple of days and see if drying the part makes a difference and if not, I'll bit the bullet and replace the part with an OEM replacement part. If the drying process helps resolve the problem, I'll post another response to let readers know however at this time I don't think it's going to work but at $560+, I'll give it a try. Oh, one last thing, the Mercedes part no in my vehicle was 000-905-06-10. The OEM part 000-905-45-03-27 claims to be the new replacement for 000-905-06-10.

If someone reading this has any more (or more accurate) information on diagnosing the blind stop assist detector please add that info to this discussion. I did question a Mercedes dealer parts representative about this issue, and he seemed to agree that the sensor on the bumpers are not used for the blind spot assist feature and that the detector is most likely the cause of the problem.
 

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Outstanding Contributor W221 Moderator
2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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Hi TRut! Due to the model-specific nature of these systems you might get a more precise answer from the GLK forum;


Early W221s used sensors hidden behind the bumpers front and rear. Later models had a combination of the hidden sensors and those embedded in the bumper for the various functions (blind spot, parking assistance, distronic, etc.)
 

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dlafever, thanks for the quick response. Since my post I now seeing that the blind spot assist feature is much more complicated. I just learn that my vehicle uses something Mercedes calls Active Blind Side and its tied to a lane keeping assist feature. It sounds like there's also another module in the front of the car. It's becoming quite clear that it's beyond any simple diagnosis. I also looked at a Mercedes video describing the feature in a simplified high level overview and it illustrates the use of other sensors just as you indicated. I did looked at the GLK forum you suggested, but didn't find anything specific that gave me any more insights, other than seeing that people are indicating that the dealer themselves are having issues solving problems with this issue (not reassuring!) That said though, the right way for me to proceed is to go ahead and take it to the dealer to diagnose the problem. I was hoping that it would have been a simpler problem to solve and that I could save some bucks. My fear is that this is going to be a very expensive fix, based on what some folks have said. Again, thanks.
 

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Okay, so I gave up one the problem. So I put the blind spot detector that I took out back into my vehicle. It literally took 2 minutes or less to reinstall it. So for grins, I started up the vehicle and noticed that the error message "Blind Spot Assist Inoperable" didn't come up. This had been a solid failure I got everytime I started my vehicle since the problem first began and the message would pop up easily within the first 15-30 seconds after starting the car. I waited about 2-3 minutes and it still hadn't returned. I ran back into my house grabbed my wallet and took the vehicle out for a 7 minute test and the problem has not reoccurred and the blind spot feature was working correctly.

It's possible, I haven't really fixed the problem, and for whatever reason the error its working now. I just wanted to explain to folks on what I did, and maybe its a fix. If you follow the thread, you'll see that all I did was to take out the sensor, cleaned it (although it really wasn't very dirty looking), place the sensor in front of my furnace register (70 degree) for about 24 hours and put it back in. Again, it's possible it'll come back, but for now, I'm excited that the problem is gone. I'll post a response if the problem reoccurs in the next day or two. This might give folks a simple inexpensive thing to try.
 

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Outstanding Contributor W221 Moderator
2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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Not impossible for these connectors to get a little crusty, a simple disconnect/reconnect a few times might just cure what ailed it. Here's hoping many miles without your error above!
 
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