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AP not resuming speed after phantom braking event?

Az_Rael

Supporting Member
Supporting Member
Jan 26, 2016
5,653
8,941
Palmdale, CA
This behavior seems to be newish to the latest software on my car (2020.28 6). I get a phantom braking event, so I put my foot on the throttle to recover, but the car doesn't resume to the set speed for several miles.

The speed limit is being detected correctly, the set speed is the same, and no obstacles are on the screen.

It was bad enough today that I put in a service ticket, but was wondering if others are seeing this behavior?

You can see in the photo below taken several miles after the original braking event, I am having to keep my foot on the throttle to maintain speed with no objects, correct set speed and correct speed limit detection. I tried tapping on the speed limit sign to no avail, it just randomly sped back up eventually. Only other way to fix it is to disengage and re-engage AP.

20200825_092343.jpg
 

mtndrew1

Active Member
May 12, 2015
1,371
3,883
Gardena, CA
I’m experiencing similar behavior.

I’ve found that if I watch the displayed speed limit at a known problem location (the 110 express lane at 39th for example) it will switch to a 25 MPH display for a brief moment then switch back to 65 MPH but the car honors the glitch speed for a while. Like you I need to override with the accelerator.

Nearly 100% of my phantom braking is due to this speed limit issue or the car mistakenly highlighting a car in an adjacent lane thinking it will be merging into my lane and slamming on the brakes to create a merge slot for that car.

I find these two issues maddening and borderline dangerous. I’ve taken to hovering the accelerator to prevent these random slow downs.

My car is also drifting so far over the line on gentle freeway curves that it runs over the botts dots but I guess that’s another thread. All of these issues on my car are relatively recent regressions in 2020.
 
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Az_Rael

Supporting Member
Supporting Member
Jan 26, 2016
5,653
8,941
Palmdale, CA
This happens to me if I have the accelerator pressed even a tiny bit while hovering over it.

It won't get back up to speed if you are pressing the accelerator? That seems like new behavior, it used to speed back up once whatever caused the initial reaction goes away.
 

Az_Rael

Supporting Member
Supporting Member
Jan 26, 2016
5,653
8,941
Palmdale, CA
New I’m experiencing similar behavior.

Glad it is not just me. Today it happened with zero cars nearby and at a point it has never happened before, so pretty sure it wasn't a speed limit problem. I can handle the braking events as much as I hate them, but this new behavior takes the frustration levels very high when the car won't recover.
 

mtndrew1

Active Member
May 12, 2015
1,371
3,883
Gardena, CA
Glad it is not just me. Today it happened with zero cars nearby and at a point it has never happened before, so pretty sure it wasn't a speed limit problem. I can handle the braking events as much as I hate them, but this new behavior takes the frustration levels very high when the car won't recover.

It’s really alarming.

My maddening autopilot issues are:

- This speed limit issue

- Lane centering has become really bad on gentle highway curves, often drifting super close to the K-rails dividing the highway (405 north carpool lane around the airport for example) or over the line and dots.

- The handling of two lanes merging into one and autopilot trying to snap straight to the center which is completely nuts for merging onramps when I’m in the right lane.

- Autopilot mistakenly highlighting adjacent cars and reacting to them, sometimes dramatically.

These seem like things that many people must be experiencing and reacting to (overriding) on a daily basis so why these hotspots aren’t being identified by the autopilot team is beyond me. Don’t they also drive these cars every day and get irritated by the same crap?
 
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john5520

Member
Mar 3, 2020
990
774
Florida
It won't get back up to speed if you are pressing the accelerator? That seems like new behavior, it used to speed back up once whatever caused the initial reaction goes away.

No, for me it doesn't. I have to take my foot off the accelerator completely for it resume controlling the speed. As far as I can remember, it's always behaved that way.
 

Az_Rael

Supporting Member
Supporting Member
Jan 26, 2016
5,653
8,941
Palmdale, CA
No, for me it doesn't. I have to take my foot off the accelerator completely for it resume controlling the speed. As far as I can remember, it's always behaved that way.

Weird. Mine used to not do that, at least up until pre virus that I recall. I didnt drive much for several months thru a few updates, so not really sure when the behavior changed.
 

serendipitous

Member
Sep 10, 2019
391
622
Maryland, USA
Mine started doing this (I think) recently as well, on 2020.28.6. Haven't had a chance to see yet on 2020.32.3. It's aggravating, it's like TACC/AP gets nervous after these phantom events and refuses to speed back up. Cancelling and immediately re-engaging resolves it, FWIW.
 

Bazza

New Member
Feb 2, 2019
4
1
Gold Coast
This behavior seems to be newish to the latest software on my car (2020.28 6). I get a phantom braking event, so I put my foot on the throttle to recover, but the car doesn't resume to the set speed for several miles.

The speed limit is being detected correctly, the set speed is the same, and no obstacles are on the screen.

It was bad enough today that I put in a service ticket, but was wondering if others are seeing this behavior?

You can see in the photo below taken several miles after the original braking event, I am having to keep my foot on the throttle to maintain speed with no objects, correct set speed and correct speed limit detection. I tried tapping on the speed limit sign to no avail, it just randomly sped back up eventually. Only other way to fix it is to disengage and re-engage AP.

View attachment 580519
Had the same problem twice today during road trip in Qld Australia. will report it tonight. Been getting a few phantom breaking events today. Hardly worth using this feature if you can’t relax and enjoy the ride.
Still enjoying my M S every day!
Regards to all:
Bazza from down under.
 
Sep 10, 2017
446
429
Outside
Had this happen on 2020.36 also. Car passed an exit, speed changed from 70mph to 40, I had to tap the speed limit sign on the screen to resume the correct speed. Strange, it was only this one exit on my daily commute. There also were no speed limit signs posted by the exit ramp or anything like that.
 

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