My passenger side blind spot assist is giving intermittent false positives as I turn on the signal to turn right. It's as though it's reading hedges or fences as vehicles in the blind spot.

This is my second W212 and have not experienced this before on either car.

Anyone else have this issue?

 

While I don't have this feature, I seem to recall the manual warning about how other objects could give out a false reading. MB just doesn't want you running into any hedges or fences.

 

I have never had a false positive from the right that I can recall. Maybe make sure your sensors are clean?

 

My blind spot failed on me -- the harnesses were corroded and they were all replaced under warranty -- this was 1500 miles into ownership of my 2014 E550... would get those checked out, there's a bulletin for this

 

I had the same issue on one of my cars, a simple fix but dealer visit is required.

 

Thanks Peter and YYZ.

 

Same here - corroded parts were replaced under warranty. I had intermittent failure of the blind spot, i.e., not functioning and then complete failure. No false positives like the OP but I could imagine how corrosion could give you false positives.

 

Shows BSD red triangle activated with no cars around.

I am having the exact same problem with 2013 E350. Been to the dealer three times. Still happens at random times. Dealer has:
1. recalibrate the blind spot and parking sensors.
2. Checked wiring and installation of the sensor. Claims no faults found and cannot replicate problem. I even provided a photo of the red triangle on which showed no cars in rear view mirror and parkland to the right - no fenses or nearby shrubs.
3. Has advanced two B. S. Reasons:
A. Repainted bumper cover causes false readings. Not true, since both left & right sensors worked correctly for a couple of years after the dealer replaced a damaged bumper.
B. Some form of electronic emissions are causing the error. Not true. The false positive has happened in a regional park where even cell phone doesn't work. Also on freeway with no other vehicles anywhere.

I am at my wits end as my CPO extended warranty expires in 9 days on 10/31.

 

That is common that unqualified technician will wait you to the end of warranty and then kill you by dropping parts on the cash you still might have left.
But you did open the work order with them and they failed to fix it? Call MB USA hotline for assistance.

 

I was under the impression that CPO does not cover driver assist problems, which would include BSD. Am I wrong on this? It is not a listed component in the CPO paperwork

 

It covered mine. I had false alarms and they found bad passenger side sensor and replaced. Car had a code stored for it.

 

My CPO extended warranty has covered absolutly everything. Had some fading on one piece of the rootwood dash. They replaced ALL the wood trim in the passenger compartment. The blind spot assist visits were also covered by CPO extended warranty. I also have wheel & tire warranty which has replaced three tires and refinished six wheels. Had oil leaks from seals around the engine two times. Last time they replaced the engine wiring harness which would have been around $4000 without the warranty. Car only has 70,000 miles.

 

My problem is that no codes were stored.

 

The blind spot sensor is not accessible from outside. My understanding is that it is a radar-like technology and is behind the bumper cover.

 

Yes, what we used to call the fender is now the bumper extensions onto the fender/wheel well area. The units are behind that

 

I have the same issue that the OP describes with 'false positives'. The history on my car is as follows:
- was rear ended a couple of years ago. Before this, the system always functioned as designed.
- the repair company 'touched up' the bumper cover and re-sprayed. In hindsight, I'm wondering if I should have insisted on a new bumper cover, since the blind spot system sounds very sensitive to even paint thickness??
- going into winter after the repair, the blind spot system stopped working on the right side. I disassembled the system, and found extensive corrosion inside the sensors (see attached pictures)
- after replacement of both sensors with new units, the system worked again. However, in colder weather I'm getting the same 'false positives' that the OP describes. It could be related to road dirt collecting on the sensor?

Please note that my car has seen a number of Canadian winters, so road salt probably is a factor in the corrosion of the sensors. Still disappointing that these sensors seem to be a common failure point due to moisture ingress.

I'm curious if anyone has any tips related to the 'false positives' other than cleaning the sensors?

 

I phoned MB USA customer assistance a d the rep stated that responsibility for repairs rests with the dealer and that they can only replace a part if it throws a code. She will escalate to her manager and they will phone back on Monday. This is our second e350 and we have used the same dealer for service. Starting to lose confidence in MB.

 

I have exactly the same problem on my 350 cdi 2010. Have taken both sensors down and cleaned them, changed sides since the sensors are the same from right to left. Still the same problem.

Disassembled the cable harness but can see no signs of corrosion on neither cable harness nor sensors. Wondering if I should change the cable harness and see if it helps.

Terrible annoying when it is dark outside and it starts to flash in the rear view mirror.

 

Getting false positives as well on the rear right side. Just sprayed the vehicle all over with water and I'm still getting this issue. It does not say blind spot assist inoperative in the dash, but while driving it gives false positives, brakes the vehicle, and tightens the seatbelts. Anybody know how much these sensors go for from Mercedes? They're closed now so I guess I'll call in tomorrow.

 

$600-800, IIRC... I replaced one on our E550 along with the harness as it had corroded at the connector. Found used sensor on eBay for <$200 and a new harness from dealer for $100.

 

Just got underneath the car, got a wet paper towel and cleaned it well. SO MUCH DIRT. Took it outside and got and rinsed the sensor to get rid of more dirt that was on the sensor. I did this knowing water damage could damage the sensor, but I just took it for a test drive and all is well. I took a look at the left rear radar sensor as well and it wasn't nowhere near as dirty as the right one, so I just left it alone.

 

Yup, they get dirty and act erratically. Their location is susceptible to collecting road grime. Hopefully an easy fix for you.

 

I don’t think it is the blind spot assist doing it. It probably is the collision preventing system. Blind spot assist warns but I don’t think uses brakes other than the active blind spot assist use brakes for steering.

Collision preventing system use brakes to slow car down and tightens seat belts if it thinks collision is about to happen.

Anyway, these systems use the same sensors in the corners of the car though.

 

Active lane holding is applying brakes to keep the direction.
But with those cars reading coffee grinds is not going far.
Get proper scanner and read the codes.

 

I had this problem as well, on both sides. The solution I've found was similar to what others have done above, remove the unit, use contact cleaner on the connections, wipe the face of the sensor down and reinstall. This has solved the issue and hasn't come back for over a year. It helps to get a power washer and spray down everywhere under the car as dirt and grime do build up, but don't get to close with the pressure washer as you could damage seals.