Hey all,
Recently purchased a (some-what high mileage) 2014 ML350 4Matic. Had it about and month now and have a strange issue that has appeared.
Problem:
When starting the car, the dash will show the yellow error message stating "Blind Spot Assist Inoperative". After clicking "OK" on steering wheel, message disappears and does not re-appear until vehicle is started again. No warnings or errors in dash message system (Please see pictures!).
Symptoms:
None, other than the dash warning. Blind spot works as intended. Both sides work accurately and perform as intended. No other system is affected. Lane-assist, and all other functions work 100% with no issues or warning messages.
Attempted Fixes & Results:
I thought maybe beings the car was driven during out winter snow storms, maybe some sensors were dirty and were causing errors. We went through a quick car wash, and the yellow message no long appeared. We made 2-3 stops with no more message and the system performing as intended. Car sat for a while, and we went on another trip. The message then showed up again. I noticed the driver side mirror light quickly turned red (passenger yellow as normal) and then changed back to yellow. The message on the dash disappeared itself without pressing OK. System worked as intended.
The Question & Concern:
Is something failing? Why is the message showing up but everything works? The wash seemed to help. Should I do a more in-depth self-wash and see if this improves? I don't have an issues getting a diagnosis from the dealer, but I'm afraid they will either say they can't find an issue and/or they will state the entire system is bad and want thousands to repair when it might just be something simple.

Included are pictures of the dash after pressing "OK" and clearing message right after start up. Blind spot is still able to be enabled/disabled.

Showing blind spot active. When pressing OK, successfully disables and re-enables system with no errors.

Showing no errors/messages in information/service tab of dash screen.

 

Your sensors may start failing. If you don't want to spend any money, I will just disable it for now.

 

sounds like the start of the blind spot sensor failing. I encountered the same thing, at first just a minor nuisance once in a while with the error you're getting, over time it became more frequent and then the blind spot feature would only work sometimes. Let the car sit indoors for a while and dry out, when you start it up it most likely will be fine, until again it encounters some moisture and the error will come back.

Some people have had success by drying out, cleaning and sealing the sensors vs replacing them.

 

Bumper. When it warms up a little I figured I'd do a really good detail on it and check all the connections and whatnot, assuming it doesn't totally fail before then.
If failure does happen, if you turn off blind-spot will it stop warning messages from showing on the dash, or do you get those regardless?

 

I'm not sure as I haven't tried disabling it. If I disabled it I'd probably forget about it and never replace the sensor, but I intend to replace the sensor and get it working.

 

Please everyone call MB customer service. The blind spot assist sensors are not sealed properly for 2012-2015 W166 ml350. I am really scared now to go for a car wash or when it snows. What’s the point in paying over $60K with so pathetically sensitive vehicles? Who pays $2500 for parts/labor these sensors every time it goes down? The last time I went to a car wash the blind spot assist sensor and mirror actuator went bust and would not work. BTW the car wash was a touch less as well. There should be a class action suit against Mercedes for ripping off people!!!

 

I ended up taking out my blindspot sensor, im going to let it dry out and try cleaning it up and then resealing it before putting it back. I noticed the wires to the connecter are showing some of the internal wiring and that may have also been what's causing the blindspot error. I've ordered new connectors and in the meantime ive disabled the blindspot, fyi you still get the error even though blindspot is disabled.

 

Where are the blind spot sensors located? How do you remove them and clean them? I have a 2015 ML350 and am having same issue.

 

Behind the bumper in the corners. Driver side is harder to get to because of a heat shield that is in the way, people say you can just bend it to reach the sensor. Passenger side one depending on how thick your arm is you may be able to reach in there and get it by just removing one screw holding the bottom lip of the bumper near the middle. It's all a very tight fit and expect to get your arm scratched up a bit reaching in there, but it's doable.

I'm thinking of attempting to remove the rear wheel well covering and then try reaching in, if the wheel well covering isn't too hard to remove and the sensor is reachable from there, it would be much easier reaching the sensors.

I got my sensor cracked open and there is definitely signs of water damage inside the sensor, good news is that the electronics look fairly clean, the water damage is mostly on the outer black plastic cover. There does look to be a bit of water damage near the pins and some water may have been entering through the connector.

 

Thanks. A bit too complicated for my skill level!