Traffic Aware Cruise Control Issue

Traffic Aware Cruise Control Issue

I have had my Model S since August 2017, and love it. I use Traffic Aware Cruise Control all the time when on a freeway and have been very impressed with how smooth it operates when approaching a slower car. I have driven the car many times up, and down, California on Highway 5, and local freeways, and never had an issue. Around March 28th I up dated the software to Version: 2019.8.3. On the 30th I headed north from Southern California to Northern California. Immediately when I engaged Traffic Aware Cruise Control, I noticed that it was behaving differently. It started getting jerky. Slowing unexpectedly and speeding up. I noticed that it was behaving this when passing slower cars in the lane on the right. The cars on the right were fully in their lane, and not drifting my direction. It seemed to be getting worse as I drove. Ultimately, when passing a car in the next lane, the brakes engaged very hard. We were happy that we had our seat belts buckled. Has anyone else experienced this issue? I have an upcoming service appointment this week, and if there is any more information, I can provide the service consultant, it would be helpful. I doubt that it has anything to do with the software update. I suspect, it’s more likely something out of align, or a malfunctioning bumper sensor.

TesMD | 07. April 2019

No, I don’t think it is a misaligned sensor because mine behaves exactly the same way. I think it is the software version causing this issue.

cfishkin01 | 07. April 2019

Mine is the same.

Munka | 07. April 2019

And another one with the same issue here :/

Also the dramatic slowing down to Lane change is new.

TeslaKU | 08. April 2019

MS90D AP2.0 - 2019.8.4 - same here

Car breaks abruptly when trying to change lanes with mild traffic. Scared to see how it would do in heavy traffic.

Boonedocks | 08. April 2019

TeslaKU | April 8, 2019
MS90D AP2.0 - 2019.8.4 - same here
"Scared to see how it would do in heavy traffic."

Not very well. I have two major freeway interchange sections on my daily commute and I have to disable NOA and TACC completely and takeover. I have genuinely tried 3 times to allow AP to do it but between the car just not being capable and roadrage it creates around me it is just not ready for prime time yet.

reed_lewis | 08. April 2019

The TACC seems to be too sensitive right now in terms of cars in other lanes. When the car in the other lane is close to the side of the lane near your car, the Tesla will slow down. While I appreciate the safety, it needs more work to make it better.

And as to interchanges, here in Mass I have never had it successfully negotiate an interchange between highways. It either hugs the right side of the lane, almost hitting the guardrail, or drives too slowly on the interchange. I always take over hoping that the video is sent to the engineers to help them fix this.

MarcelB | 08. April 2019

Ditto: we stopped using the TACC in heavy traffic (our usual commute). That was one of the best features.

We live in Silicon Valley, so a heavy traffic commute is the norm. We've noticed the same issues as you:
* sudden braking while passing a car in the next lane (or even 2 lanes)
* following distance is way further away in stop and go traffic, and very rough (my wife the NASA rocket scientist said "They really screwed up the controller : the gain is way higher than it used to be, almost to the point of chatter")
* when you "stop" in stop&go, you're 1/2 or more car lengths away: just enough for someone to try and cut in

S75RedRidingHood | 08. April 2019

During my recent two weeks trial in my Model S, I experienced the same behavior on freeway. It is make me feel unsafe because this could be a cause for read ended. That is why I have decided to hold off the auto driving option purchase until later. I would rather pay more for the software that actually work rather beta version.

TranzNDance | 08. April 2019

I've reduced use of auto-pilot since 2019.8.3. Good thing the car is a joy to drive manually.

diamonds2 | 08. April 2019

The above mentioned behavior began for me with 2019.4.2. Upon reporting the issue to the my local SC, they pushed me 2019.4.3. The issues got slightly better but TACC is not as smooth as it was before 2019.4.2

jerrykham | 08. April 2019

Ditto to the rest. just started recently. We had phantom breaking before (like with shadows of overpasses and the like) but it is a bit ridiculous now.

BPSoCal | 09. April 2019

Same here. In my case it started when I installed 5.15. I also drove many miles on TACC in LA traffic with no issue, after that software update, I got motion sickness from using TACC.

The 2019.12 update seems to mitigate *some* of that erratic behavior, but it’s definitely still not as smooth as it once was. I’m still not as comfortable using it as I used to be.

mdmgso | 09. April 2019

Ditto. Same problem whether passing slower traffic on right or left.

TeslaKU | 09. April 2019

In testing TACC at night with light traffic, I noticed something. It feels like the Tesla has two modes: accelerating and breaking. There really is no coasting. Whereas we humans would let the car coast before accelerating or breaking, the Tesla is either doing one or the other.

MS90D AP2.0 FSD 2019.8.5

ens | 09. April 2019

Yep, experiencing similar issues with TACC since about three updates ago (since maybe around a mid February update). On a 2018 S100D. Never had this on my last S85. And don't recall a issue to this level on current S prior to updates about two months ago. Very frustrating driving in rush hour on the 405. Phantom breaking and sudden breaking, from what appears to me to be related to a car in the next lane, sometimes next to me sometimes a car length up ahead in the next lane. Also slowing way below the speed setting when a car is way way up ahead in the same lane - have car set to 1 distance, but it slows down, e.g., to 55 instead of 65 when the car in the lane ahead is still 8-10 car lengths away - I have to override it. But its the sudden ghost breaking that makes using TACC scary, and makes it look like I'm break checking the person behind me ... which can lead to serious issues too.

foster.steve | 09. April 2019

Last night I received the 2019.8.5 update, and went out and tested myTACC, and all my issues cleared up. I passed cars, semi’s and exits without issue. I even edged a bit closer to a couple semi’s as I was coming up on them, and I had none of the sudden braking, or jerky sensation, that I was experiencing before. I’m back to being a happy camper.

Munka | 09. April 2019

@steve, Awesome I am now back to hoping for an update. Have a SC appointment in 2 weeks (for an unrelated poorly fitted spoiler), will ask them to update it if not done automatically.

@S75RedRidingHood Don't give up just yet, its normally amazing! It's just a bit patchy with this update, I'm sure they are taking onboard the feedback and correcting it.

Chris-L | 10. April 2019

I just finished a 1,200 mile trip from South Florida to South Carolina and back. My car was 3 weeks old at this point with 2019.8.3 software. The car behaved exactly as reported here. Very disappointing as I had traded in a 2016 Model S that NEVER behaved in this way in ~34,000 miles. I've posted a problem report and sent an email describing the problem to the local service techs. I also have 2019.8.5 but have not had a chance to test it. Encouraging post from foster.steve - thanks.

acerfacer | 10. April 2019

@foster.steve .... I also own a 2018 S 100D running on 2019.8.5

Drove Portland/Seattle round trip last week. Flawless performance on both TACC and NOAP.

teslarama | 10. April 2019

Elon..please fire every employee who is testing TACC and save some cash yourself.
This is not a corner case at all.
One hour will see the sudden braking problem.
This is the one feature I loved and you guys messed it up this one too.
Whenever you folks release new SW to improve those stupid features like NOA...make sure you dont mess up TACC.

2017 MX AP2 FSD

teslarama | 10. April 2019

Some people are not seeing this issue...may be only AP2 cars have this issue?
AP2.5 is fine?

I have 2019.8.5

dougk71 | 11. April 2019

I have a 2019 100 D 2019.8.5 HW 2.5 and this sudden breaking issue occurs about once in every 100 miles of driving. The braking is not exactly unwarranted since the car is detecting a situation that needs attention. I surmise the issue is that a human driver can predict the future and can expect the obstacle that is causing a need to brake will quickly move out of the way The automation only has the immediate present from which to make a decision so hard braking is warranted only to find out in a second or two hard acceleration is needed since the issue has gone.

teslarama | 11. April 2019 you definitely feel 8.5 is more sensitive compared to 2018.50.6 release right?
In my one instance there was nothing nearby.
As somebody stops too much away from front vehicle on the stop and go traffic, waits longer to start after the traffic moves and starts with jerky motion compared to previous one.

happy to heat that 2.5 also has the same issue. Otherwise...they might take more time to fix this.

diamonds2 | 11. April 2019

June 2017 MS100D HW2 VIN 200XXX:

Before the 2019.4.2 update my TACC was working great. Once I received the 4.2 update I had all the negative issues described above. 4.3 brought some improvement and 8.5 brought even more improvement. But it's still not as "silky smooth" as pre 4.2

wefdenver | 11. April 2019

I just got my MS 75D last week. The TACC does the breaking when a car is in the other lane and I am on release 2018.39.6. Still waiting for my first upgrade.

dougk71 | 12. April 2019

I like 2019.8.5 it is just as it expands the situations it can handle it moves into areas that aren't always straight forward or that maybe handled in different ways. Humans evolved an ability to predict....where and when food would be available and where and when danger may occur. We are good at anticipating what other drivers pedestrians etc might do in the next second or two. If it is potentially dangerous right now but we anticipate in one second the danger might pass we try to finesse it into a single action like slowing down non aggressively. The automation will brake hard and accelerate hard shortly there after.. no finesse ..a jerky action. I really expect A.I. can't do much about this it is more than deep learning it is instinct.

dougk71 | 12. April 2019

I remember an example of image recognition for target acquisition. An anti-tank gun could recognize the image of a tank. However if an image of a tank was painted on the side of a cow..the system shot at the cow. Human instinct tell us that you can't see tanks through cows. The win from Autopilot 2019.8.5 is that is takes much stress away from interstate highway driving with the worthwhile trade off of some quirky no obvious reason action once in a rare while.

brianp6621 | 12. April 2019


I have had my 100D for just over a year. I commute an hour each way on 101 in the bay area. I use the carpool lanes exlusively so I am often (and oftentimes not) driving a decent speed faster than the lane to my right. In the beginning AP handled this PERFECTLY. However over the last few months (my issues started earlier than OP describes) I began having phantom breaking due to the cars in the lane to my right. I actually have to keep my foot poised over the accelerate to quickly recover from this to not get rear ended or at least not cause a ripple slow down in the carpool lane when this happens.

I have also noticed (don't know if it was like this before as I never paid close attention) that the car animations on the display behind the steering wheel, seem to show the virtual cars wavering towards the line and even crossing over it as I catch up and overtake them, even though the physical/actual cars aren't wavering at all and are clearly in their lane. I can watch this over and over. They screwed something up with the image recognition of the cars/lane markers recently and it makes this originally butter smooth implementation, far less desirable.

Mchenry7 | 12. April 2019

Same issues others are seeing. Can confirm that the excessive, mostly random braking for cars to the right, is affecting both our 2017 MS90D (2019.8.3) and our new M3LRD (2019.8.5) equally. Started about 2 revisions ago. Renders TACC almost useless in Bay Area commute traffic. The fear of getting rear ended in the commute lane is far too high now. It is no longer the stress reliever it used to be. Another 1 step forward, 2 steps back situation. Really unfortunate. Hope they get it sorted out soon.

davemount | 14. April 2019

Ditto. SF Bay Area. 2017 S 75D. Same problem since the infamous update.

RanjitC | 15. April 2019

2016 P90D with AP1 seeing the same problem

badjuan | 15. April 2019

I too suffer all that has been posted. Having passengers sensitive to abrupt motion changes especially unaware ones, they are favoring riding in a different vehicle. Frustrating for me since I would like to know why this happens and I just tolerate it in hopes that Tesla would alleviate this problem soon!

teslarama | 15. April 2019

I haven't see anybody complaining about 8.5 on model 3 forum. Is this problem only applicable to MS and MX?

BPSoCal | 16. April 2019

I'm on 2019.12 and the problem hasn't been solved. Also AP 2.5. I've done several bug reports and Tesla tech support asked me to schedule a service appointment to make sure it's not hardware related.

I told them "trust me, nothing in the hardware has changed, but this issue started with the 5.15 software update I got in early march."

rsrivast | 16. April 2019

I am also see thing behavior after 2019.8.5. I found this to be quite dangerous as I might get rear ended due to sudden unexpected hard brakes. This is quite prominent when using HOV lane and the traffic in the next lane is significantly slower. Tesla please FIX!

teslarama | 16. April 2019

The OP says..all the issues he mentioned are gone when he updated to 8.5.
I have 8.5 and I encountered all the issues OP mentioned.
Today..on my commute I did not see phantom braking.
I do feel it is more sensitive and not smooth like before. Still stops far away and starts in a jerky motion.
But I did not see phantom braking.
We are in deep shit now...this is not that easily reproducible and affecting only a section of people.

ronsrq | 16. April 2019

Same here with 2019.8.5

diamonds2 | 16. April 2019

Same as teslarama.

I miss how smooth everything was pre-2019.4.2

BPSoCal | 16. April 2019

It shouldn’t be that hard. Cut all the new code introduced for TACC in newer updates and paste the old code into it.

teslarama | 16. April 2019

The jerky start and stopping bit far away..all those can be easily reproduced and easily fixed.
My only concern to reproduce phantom braking.
In my last 2 commutes...I did not see phantom braking.
I can explain why the car is braking every time.

Do you folks still see phantom braking frequently?

Chris-L | 16. April 2019

As foster.steve reported, 2019.8.5 fixed his problem. It also fixed mine. TACC now behaves as it did on my 2016 Model S90D. No longer "afraid" of cars passing, or being passed, in adjacent lanes. I also tried out Navigate on Autopilot - surprisingly weird. It works as advertised but I'm not sure I'm ready to turn over my lane changes and highway exits to my car .... at least not yet ;-)

teslarama | 16. April 2019

@Chris-L...thanks for the confirmation.
So..8.5 is good for some and not for all. This makes things complicated.
Do you have AP2.5 or 2.0?
Just to don't have all of the following issues.
phantom braking, stopping bit far away from the front car, jerky starting from complete stop, bit laggy to start from the dead stop

rsrivast | 17. April 2019

All problem exists in 2019.8.5 (2018 AP 2.5).
- sudden phantom braking.
- jerky ride / start due to frequent braking - was smooth before.
- gets confused with slower moving traffic in adjacent lane
Will tweet to @elonmusk...see if he responds :)

teslarama | 17. April 2019

@rsrivast..thank you.
That's a relief for AP2.0 owners like me.
As long as the problem is generic...they will fix it.
Not sure how this passed their QA.
I did see phantom braking yesterday again.
One hour commute in bay area should easily reproduce all the issues.

teslarama | 17. April 2019

Seems like model 3 owners also have the same issues.

fentonite | 18. April 2019

There are so many areas behaving badly in the this release, I wonder if this isn't a general corruption issue. @BPSoCal How do you file a bug report?

BPSoCal | 18. April 2019

@fentonite - I did 2 things, during several of my drives, after each occurrence of crazy accel/decel or phantom braking, I pressed the talk button on the steering wheel and reported the issue there. "Bug report, TACC acceleration and braking issue"

Secondly, I sent a feedback email via the Tesla website describing the issues in more detail. I got a response within a couple of days and they want me to take my car into a SC to make sure it's not hardware related.

Still, I'm not using TACC right now, it gives me motion sickness. It's a step back from what it used to be.

PagemakersS75 | 18. April 2019

@rsrivast I have all the problems you describe and in addition the app fails to connect to the car every few days.

Worst update in a long time.

marika.appell | 19. April 2019

I have just tried version 2019.8.6 with Navigate on autopilot on I95 in Florida.
I finally got to try the new autopilot yesterday. On I95 going south in light traffic it performed flawlessly. Changed lanes when approaching a slow car and returned to the middle lane. Got to the far right lane and exited I95, about 25 miles on autopilot without intervention.
On the return trip on the turnpike, only 2 lanes, during rush hour, it was a disaster. It would try and move to the passing lane, put on signal and the car on the left would close the gap. After several tries the guy behind said enough of the hesitation and pulled around me. I disconnected and passed myself, it needs more aggression even though I have it in Mad Max mode. A second try when traffic thinned resulted in wanting to move into the passing lane but hesitating. It would continue to move half way then abruptly return to the left lane. After about 4 tries I took control as I figured the guy I was trying to pass was calling the cops about a drunk driver. There was no upcoming cars and I figured that it got confused by the lane barrier thinking it was a car. I sent several "bug reports."

Still a work in progress but very impressive for long distance travel in light traffic.

UberJumper | 12. Mai 2019

New-ish (March 31,2019) model 3 owner here...

I’ve observed this as well. Interestingly enough, it seems to be the shadows. My morning commute is fine on AP, up until my route switches from an east to west direction (sun to my back), to a northerly direction.

I come out of a tunnel (in a counterflow lane), under an overpass (where I first saw the unexpected braking in the past), and then I’m heading directly north and am in the left hand (of 4) lane. In the 08:15 to 08:20 time frame in that stretch the shadows from cars in the lanes to the east are being cast significantly into the lanes to the west.

I believe the car’s software balks at those shadows especially if they are from taller vehicles.

I’m going to have to remember to pull my teslacam videos for this.

Anyone else confirm via direction of travel, lane position and time of day if shadows are a factor for them?