CX-90 Blind Spot Monitor Malfunction

https://www.youtube.com/watch?v=a1ydjD7cRx4
My son recorded the video on 5/2/2023

We were experiencing driver side blind spot monitoring system malfunction. It would randomly and falsely warn us of a car in our blind spot when there isn't. It sometimes just stays on for no reason when the car is in motion and even when stationary.

For some reason it hasn't happened as often the last few days. Was out driving for a couple of hours over the weekend trying to record it happening again, but the BSM was working fine for the entire 2 hours.
 
I experienced this just yesterday for the first time, and it is gone today. Yesterday it occurred in two different trips (driving cycle). Yesterday was rainy and today is a nice day. So track if it seems to only occur during rain. The next time it happens, I am going to try turning the BSM sensitivity to near / low to see if it still occurs.

I was mainly seeing it come on and just stay on for long periods of time.

Edit: Just saw your response in the other thread, sorry for the double post.
 
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I’m also having BSM false alerts on the drivers side. Happens off and on with no apparent rhyme or reason.

Some YouTube car reviewers have noted this as well.

I have a feeling a lot of owners will be reporting this in the coming months so I’m confident Mazda will have a fix.
 
The one thing that makes me at least not get too frustrated by the BSM false positive, is that when I expect it to alert me, it seems to function fine.

But I agree, this will need fixing. As long as Mazda is committed to working through these growing pains, its sort of the price to pay for being first in line.
 
I think the new system of CX-90 is likely too sensitive.

From my '14 to '16 to '17 to '22 (I have four Mazdas), the newer BSM detects vehicles farer way.

Can't say I like the change. I like the ones on my '14 and '16.
 
Id say its likely that there is some kind of interferences its picking up that they didnt see much of in testing. Because this is RF based, I am sure they have the DSP capacity in the system to add some filtering to take care of the issue. The system works well for true hits in the blind spot, I think there is just some tuning that needs to happen, or it also could be a messed up batch of sensors.
 
As far as I can tell, adjusting this setting doesn't seem to effect the false positive (sensor alerts come up and hold with nothing there, on open flat country roads) that I am seeing.
 
BSM is based on two small EM radars located at both corners of rear bumper.
I had it since my '08 CX9.... it was very rare at that time.

I think the calibration or its software is bad (noises not filtered out properly).
Setting in MID might not help. That adjusts for distances only, not noises.

My two cents.
 
Completely agree. It appears that whatever the culprit (noise floor or something of the like) for the sensors are likely dynamic, because when the system operates normally it tends to stay that way, and once it starts acting up it continues to occur / the frequency of occurrences tends to go up during that drive. My best guess is that the system encounters something that is messing with the noise floor / gain / doppler filtering loops and that is what causes the false positives.

From the bit of digging I have done on others reporting similar issues it appears to be consistently the driver side, which re-enforces the likely hood its a calibration / software thing.
BSM is based on two small EM radars located at both corners of rear bumper.
I had it since my '08 CX9.... it was very rare at that time.

I think the calibration or its software is bad (noises not filtered out properly).
Setting in MID might not help. That adjusts for distances only, not noises.

My two cents.
 
We've had our CX-90 Turbo S PP since late April and also experience the false driver's side BSM alert. After almost 1,000 miles I've determined that it only occurs between 20 mph (system activation speed) and 54 mph where it almost continuously cycles on and only briefly off. Once 55 mph or greater is reached it turns off and functions correctly at highway and freeway speeds, which is good as that's where it is most needed.

It is very annoying to have it alert for almost every left turn around town, on two-lane roads and even in our subdivision where there clearly aren't cars next to us.

Hopefully they determine a fix soon.

Has anyone contacted Mazda customer support or their dealer to report the issue?
 
We've had our CX-90 Turbo S PP since late April and also experience the false driver's side BSM alert. After almost 1,000 miles I've determined that it only occurs between 20 mph (system activation speed) and 54 mph where it almost continuously cycles on and only briefly off. Once 55 mph or greater is reached it turns off and functions correctly at highway and freeway speeds, which is good as that's where it is most needed.

It is very annoying to have it alert for almost every left turn around town, on two-lane roads and even in our subdivision where there clearly aren't cars next to us.

Hopefully they determine a fix soon.

Has anyone contacted Mazda customer support or their dealer to report the issue?
I too have noticed it seemed speed related. I share you sentiment of getting annoyed by alerts for left turns around town.

So I used one of the Mazda App "Give us Feedback" prompts to dump my CX-90 thoughts. Ill be going in to service department to pick up an oil filter / crush washer as I always change out engine break-in oil at 1k miles. Ill bring it up then, and have them make note of it.

Hopefully by the first free oil change done by them they have a fix and we can apply it then.
 
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I too have noticed it seemed speed related. I share you sentiment of getting annoyed by alerts for left turns around town.

So I used one of the Mazda App "Give us Feedback" prompts to dump my CX-90 thoughts. Ill be going in to service department to pick up an oil filter / crush washer as I always change out engine break-in oil at 1k miles. Ill bring it up then, and have them make note of it.

Hopefully by the first free oil change done by them they have a fix and we can apply it then.
I chatted with Mazda USA Customer Service and they noted it, but said that it should still be diagnosed and reported by the dealer as well. The CSR I chatted with didn't say if they were aware or if there was any fix in the works.
 
Currently I am just trying to get videos of it when it acts up, so I can easily show what is going on to the dealer when the time comes.
 
Same problem here, got my CX-90 PHEV last Thursday, immediately on Friday I noticed this issue. It has been on and off. Mostly happening when driving below 50mph, which is mostly the speed I am driving this car at locally. Pretty disappointed though about this issue since every single Mazda I've owned since 2007 all had issues out the door but this one is safety related and needs to be addressed ASAP Mazda!
 
My driver side malfunction / bsm false positive seems to be getting worse. When I first noticed it, it was coming and going, occasionally holding in the on/alert state. Now it seems that when it starts triggering it only holds for long periods of time. Thankfully it works fine over 50 mph, but its annoying to have many left turns give the extra alert driving around town...

I am going to try taking out / moving the scissor jack which is right next to the radar sensor and see if this issue is actually a side lobe interference issue from the jack.
 
I have had BSM since my '08 CX9.
BSM issues have been rare.

One problem I have heard before on the old CX9 forum was that the radar sensor was not attached to the inside of rear bumper properly. That causes EM wave to bounce back spuriously and triggers the light to turn on. If so, that would be an assembly issue, which does not surprise me since CX-90 is new (1st yr). Guessing here, of course.
Good luck. Please alert the dealers.
 
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