Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Cruise Control and Autopilot Suddenly Decelerates

This site may earn commission on affiliate links.
I bought a brand new 2022 MXLR in April 2022 that now has about 7000 miles on it. On a couple of recent trips - I have used both cruise control and autopilot (steering assist) and in both cases the car suddenly DECELERATES from 85 to 70 (in the most extreme case, usually it's brief and drops from 85 to 80 or so, but its always jarring in how hard it brakes). I heard they recently went to an 'all camera' system to interpret surroundings and whether or not the vehicle needs to brake or not... So it could be certain conditions (driving into sun, driving up a hill just before reaching the crest, inclement weather, etc) but it has happened to me more than a dozen times in one trip (1200 miles total).

It's incredibly dangerous, not only the sudden slow down and my own reaction, but if there happened to be a car behind me, traveling a bit too close - it could easily cause an accident. This problem is a dealbreaker for me - anyone else have this issue, and have any idea what to do about it?
 
Yep, My 2017 Model S has the same issue. It's been going on ever since the front radar was determined to be unnecessary. The radar has been disabled for older cars with FSD and the newer cars no longer ship with radars. The software thinks it sees something worth braking for when there is actually nothing there. Our 2018 Model X without FSD still has and uses its radar and doesn't have this issue.
 
Upvote 0
...anyone else have this issue, and have any idea what to do about it?
Old news:


You can go to NHTSA and add your case to it.

In the meantime, if you don't like Tesla's advanced technology then you can drive manually and don't use Tesla cruise control or Autopilot, FSD.

Historically, all companies that use radar have phantom brake problems. Some more than others.

Tesla used to have radar too so to solve the phantom brake problem, it decided to ditch radar and use pure vision instead.

Now you are in pure vision and that's the consequence of implementing a theory without first testing it. You are now a tester for pure vision.
 
Last edited:
  • Like
Reactions: macchi
Upvote 0
This is called Phantom Braking. It is a thing and is not getting better. Now that Tesla has eliminated radar, even cruise control uses the same programming as Autopilot and has issues with Phantom Braking. I wish there was an option to enable dumb old cruise control like our Roadster and 1st Gen MS had. Alas this is not to be.
 
  • Like
Reactions: SSonnentag
Upvote 0
I bought a brand new 2022 MXLR in April 2022 that now has about 7000 miles on it. On a couple of recent trips - I have used both cruise control and autopilot (steering assist) and in both cases the car suddenly DECELERATES from 85 to 70 (in the most extreme case, usually it's brief and drops from 85 to 80 or so, but its always jarring in how hard it brakes). I heard they recently went to an 'all camera' system to interpret surroundings and whether or not the vehicle needs to brake or not... So it could be certain conditions (driving into sun, driving up a hill just before reaching the crest, inclement weather, etc) but it has happened to me more than a dozen times in one trip (1200 miles total).
Any chance this could be a false read of a speed limit sign? I've noticed that if a speed limit and a truck speed limit are placed side by side, my car will sometimes read the lower truck speed limit. It can 10 - 15 mph slower, the car slows pretty rapidly when that happens
 
Upvote 0
I bought a brand new 2022 MXLR in April 2022 that now has about 7000 miles on it. On a couple of recent trips - I have used both cruise control and autopilot (steering assist) and in both cases the car suddenly DECELERATES from 85 to 70 (in the most extreme case, usually it's brief and drops from 85 to 80 or so, but its always jarring in how hard it brakes). I heard they recently went to an 'all camera' system to interpret surroundings and whether or not the vehicle needs to brake or not... So it could be certain conditions (driving into sun, driving up a hill just before reaching the crest, inclement weather, etc) but it has happened to me more than a dozen times in one trip (1200 miles total).

It's incredibly dangerous, not only the sudden slow down and my own reaction, but if there happened to be a car behind me, traveling a bit too close - it could easily cause an accident. This problem is a dealbreaker for me - anyone else have this issue, and have any idea what to do about it?
Had this issue consistently in specific spots in 2017-2018. Some of it was vision/radar data, and some of it was map data. Having it some now with FSD beta (making my 2017 camera only), but not as bad as what it was a few months ago on the beta or in 2017-2018 before it improved with updates. I'm very used to having my foot hover over the accelerator and overriding when this happens. TBH, it probably isn't slowing down as drastically as it feels regardless, but foot over the accelerator for a quick reaction will work until/unless you accelerator into a real obstacle because it was slowing down for a legit reason and you weren't paying enough attention. Unfortunately, that does mean your foot isn't as close to the brake as it could be or in as comfortable as it could be, but I should imagine it will improve over time. Meanwhile, you could try communicating with / showing it to a service center on the off chance it is something else specific to your vehicle.
 
Upvote 0
Now it slows and brakes every few seconds to minutes for no apparent reason.
I have not heard of anyone experiencing that high a frequency of false braking while on Auto Steer; false braking events occurring just seconds to a few minutes apart. Does that happen to you over an extended period of time; extremely frequent false braking events?

I have them occur roughly once every 300-500km of driving.

I like your sig BTW. 👍
 
Upvote 0
You can eliminate incorrect speed limit detection by choosing "Current Speed" instead of "Speed Limit" in Controls > Autopilot > Set Speed.

This is what I have set and I still get phantom braking. Only Tesla would note in the manual that "Traffic-Aware Cruise Control is a BETA feature" and not give us an option of using any kind of non-BETA cruise control feature.
 
Upvote 0
Occasionally, and with cause (bridge shadows and such). Now it slows and brakes every few seconds to minutes for no apparent reason.
Is there oncoming traffic in the next lane? I get the impression from a non-FSD vision only Tesla owner that their AP is not very useful on 2 lane roads with oncoming traffic (vs divided highways where adjascent lanes travel in the same direction).
 
Upvote 0
Old news:


You can go to NHTSA and add your case to it.

In the meantime, if you don't like Tesla's advanced technology then you can drive manually and don't use Tesla cruise control or Autopilot, FSD.

That's what I ended up having to do since I do not want to get rear ended. Sucks paying $132K for a car that doesn't have basic cruise control.
 
Upvote 0
Is there oncoming traffic in the next lane? I get the impression from a non-FSD vision only Tesla owner that their AP is not very useful on 2 lane roads with oncoming traffic (vs divided highways where adjascent lanes travel in the same direction).
It's definitely worse with oncoming traffic, but bushes, shadows, tarred cracks in the road and other unidentified reasons cause slowing/braking. It's WAY better on divided freeways, but I drive 500 miles per week on mostly 2-lane highways, one lane in each direction. The really bad part is that cruise control is affected just as much as AP/FSD.
 
Upvote 0
It's definitely worse with oncoming traffic, but bushes, shadows, tarred cracks in the road and other unidentified reasons cause slowing/braking. It's WAY better on divided freeways, but I drive 500 miles per week on mostly 2-lane highways, one lane in each direction. The really bad part is that cruise control is affected just as much as AP/FSD.
I've always felt that Tesla should have an option to run standard cruise in their AP vehicles and have even turned away potential customers by informing them of the absence of that option. Hopefully the vision cruise/ap behavior will improve now the same way the radar did over several years after 2.0 came out previously.
 
Upvote 0
I bought a brand new 2022 MXLR in April 2022 that now has about 7000 miles on it. On a couple of recent trips - I have used both cruise control and autopilot (steering assist) and in both cases the car suddenly DECELERATES from 85 to 70 (in the most extreme case, usually it's brief and drops from 85 to 80 or so, but its always jarring in how hard it brakes). I heard they recently went to an 'all camera' system to interpret surroundings and whether or not the vehicle needs to brake or not... So it could be certain conditions (driving into sun, driving up a hill just before reaching the crest, inclement weather, etc) but it has happened to me more than a dozen times in one trip (1200 miles total).

It's incredibly dangerous, not only the sudden slow down and my own reaction, but if there happened to be a car behind me, traveling a bit too close - it could easily cause an accident. This problem is a dealbreaker for me - anyone else have this issue, and have any idea what to do about it?
I experienced this same exact issue the other night. Here is my experience. Navigation on, cruise set to 5 mph over (70mph). I was in the right lane approaching the off-ramp (which I was NOT taking). As I passed the off-ramp, the cruise suddenly dropped to 55 mph. This occurred three separate times. I then turned OFF the navigation and continued with the same cruise settings, and passing the off-ramps it no longer occurred.

I suspect that the car in navigation mode was "thinking" I was getting off the highway and then slowed to the off-ramp speed limit. I agree with jboston17 that this is a serious issue that needs to be addressed for safety and driver interaction. It was sudden and unexpected the first time; the rest of the drive was 100% of my attention on the speed and screen to watch if it would do it again so I could be ready to react.

Has anyone else experienced this??
 
Upvote 0
I experienced this same exact issue the other night. Here is my experience. Navigation on, cruise set to 5 mph over (70mph). I was in the right lane approaching the off-ramp (which I was NOT taking). As I passed the off-ramp, the cruise suddenly dropped to 55 mph. This occurred three separate times. I then turned OFF the navigation and continued with the same cruise settings, and passing the off-ramps it no longer occurred.

I suspect that the car in navigation mode was "thinking" I was getting off the highway and then slowed to the off-ramp speed limit. I agree with jboston17 that this is a serious issue that needs to be addressed for safety and driver interaction. It was sudden and unexpected the first time; the rest of the drive was 100% of my attention on the speed and screen to watch if it would do it again so I could be ready to react.

Has anyone else experienced this??
Were you using Navigate on Autopilot?

Were there 55MPH speed limit signs posted near/on the off ramp? The car may have picked up on those and interpreted that as the current speed limit.
 
Upvote 0
Just so I understand the consensus, is it "normal" to get sudden braking when using cruise control if the car sees another car pull out or cross in front, even if it's +300' in front of you? I could sort of understand that if I was running 75-80, however, I'm seeing it even running 40 MPH. It's always a big surprise when it hits the brakes so hard given that you are in no danger of the car pulling out or crossing the street.
 
Upvote 0
Just so I understand the consensus, is it "normal" to get sudden braking when using cruise control if the car sees another car pull out or cross in front, even if it's +300' in front of you? I could sort of understand that if I was running 75-80, however, I'm seeing it even running 40 MPH. It's always a big surprise when it hits the brakes so hard given that you are in no danger of the car pulling out or crossing the street.
"Normal"? Yes. Subject to improvement with updates? I certainly hope so. Based on my experience with one vehicle with radar that is now in the FSD beta, this behavior is new with vision only AP.
 
  • Like
Reactions: 1pinhigh
Upvote 0
Trip to Phoenix and back from Denver. Had several (at least 10 - 20) instances of severe braking. If I did not stomp on the accelerator immediately, the car would continue to slow, it seemed nearly maximal braking. No reason was apparent. Some braking instances were on long straight stretches of I-40 with no cars visible in front and none in back. Severe braking was noted whether the car was under Traffic-Aware Cruise Control, Autosteer (Beta), Navigate on Autopilot, or FSD (Beta); never when the car was being manually driven. Each occurrence really startled and scared us. We have traveled to and from Phoenix several times in past years and have never experienced this activity. 2018 MX 100D

I tried to schedule service for this problem but received the reply:
"There are no faults with any of the hardware in the vehicle and at this time these behaviors are a limitation of software in the system. A service visit is not needed at this time."

I feel this behavior is dangerous. It was not there in years past. It renders cruise control almost useless, IMHO.
 
Upvote 0
I've had the happen to me frequently in my 15MS and 18MX. And I recently notice it happening on this new route I take. It appears that there is a section with 55MPH speed limit marked and the Cruise control max speed there will automatically change to 60 and the cars will break aggressively, even there is nobody around me. Curiously, it also happened in my SO's 2023 GLE350 as well, the exact same behavior!
 
Upvote 0