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Our MS scared the living daylights out of us

Our MS scared the living daylights out of us

This is something that has happened 10 times over 3 months. Driving auto-cruise-control, on the motorway, passing a truck, when suddenly the car slammed the brakes. No reason, nothing in front, nothing on side (crash barriers). The 1st time there was a car close behind me, and I heard his tires squealing. 2nd time, there was lno one behind me. Both times I checked the dash, and there was nothing on the display that would cause the MS to act like this.

Now I'm afraid to drive with auto-cruise-control, let alone self-drive. Is this behaviour normal? The MS is late 2018 and updated to the latest firmware.

EVRider | July 16, 2019

Some people have reported the issue, but it's not happening to everyone.

The "latest firmware" means nothing -- which specific version do you have?

By the way, there's no "self drive" yet. There's TACC (which you called auto cruise control), Autosteer (which is lane keeping), and Navigate on Autopilot which will steer and propose lane changes, and make those changes if you allow it. This is still far from self driving.

murphyS90D | July 16, 2019

Keep your foot over the accelerator pedal and immediately push it if that happens. The braking will be aborted.

dir | July 16, 2019

I also keep my foot hovering over the accelerator.
I’ve documented this to Tesla with a definitive video; their answer was that this behavior is not typical, but not out of the question, and it’s documented in the manual. In my case there was a car in another lane that TACC latched onto. I agree that it’s very dangerous and I’m expecting to hear news reports anytime of accidents caused by it.
It seems to happen most often when there is an on-ramp to the right.

dir | July 16, 2019

I would be willing to bet that if Elon was made aware of this behavior (or experienced it himself), it would get fixed very quickly.

Ohmster | July 16, 2019

Used to happen at bridges (shadows), passing exits on freeways, and for slow cars in adjacent lanes.

Was also a mess when my GPS antenna was broken.

Much better on 24.1 with a working GPS.

mickel.werner | July 16, 2019

@EVrider 20.4.3. Too many acronyms. Yep, was using TACC and meant auto steering.

My initial thought was more or less as per @Ohmster since I noticed plastic stuck to the cars barrier on my left that was flapping. But 2nd time there was nothing but empty lane and no bridges.

mbirnie51 | July 17, 2019

March 2017 build, MX 75 D. Driving I-5 in CA. I've had this happen to me also while using Nav-on-AP, and most of the time it is when I'm in the right lane at the on-ramp. The other auto was far enough back in the acceleration lane, but was catching up to me, but not to the point of registering on the dash as an icon, and my MX braked hard.

I get concerned with this because I feel that at this stage of development, these situations shouldn't cause braking. I mean, if I was driving the MX without any assistance engaged, I wouldn't even let off the accelerator in that situation

sentabo | July 17, 2019

I've had that happen a couple of times. I simply stepped on the gas. It was a little disconcerting. I did wonder if the guy behind me thought I was an idiot.

Ohmster | July 17, 2019

^Nah. Folks behind us think that is the launch indicator. Brake then accelerate like a bat out of hell. :)

rweggert | July 19, 2019

I just returned from a 5600 mile road trip throughout the west and this happened to me no less than 50 times. My estimate is it would occur randomly every 10-20 trucks. I made every effort to try to understand why it was happening but it was 100% random - there was no pattern whatsoever. I simply took hold of the wheel and prepared to accelerate every time I passed a truck. Even though I was usually expecting it, it took a lot of the joy out of driving because the hard braking and slapping of the brake pedal was always unnerving.

Pbabcock | July 19, 2019

I have this same problem, I'm my own danger on the road when the car goes from 80mph to 50mpg in no time. Passing trucks and people entering the highway to the right are all signs that the car will misbehave. Online support tells me to visit a service center. Any idea of a fix coming or suggestions on what to do? My Model S is one month old.

Bill_75D | July 19, 2019

I no longer use TACC when my wife is in the car. The sudden braking for no reason always starts an "I'll never buy another Tesla" conversation.

Roger1 | July 20, 2019

I have experienced braking for no apparent reason when on TACC and Autopilot. My wife only uses TACC when driving and had the problem happen last time we went on a trip. She knows about the accelerator override to regain control but isn't happy about the solution.

I think the TACC and Autopilot software has more problems now than 6 months ago. We took a 7,200 km trip in February and didn't experience the issues we have today. A menu option to select a 'simple' version of cruise control using only the radar data to manage speed and prevent rear end collisions would be helpful.

The car is a September 2017 S100D with 2019.20.4.3 software.

SteveZzz | July 21, 2019

With my Sep 2017 Model S100D with 2.5 h/w and currently running s/w 2019.20.4.3 (same as @Roger1), I put on over 1,000 km each and every week, almost all of it on the highway and almost all of it with Navigate on Autopilot (NoA). I currently have over 75,000 km on the car, and probably 65,000 of those km are on NoA or Autopilot.

I can not be sure of when it started (i.e. with which s/w version it started), but I get the "slam on the brakes" thing happening about 2 to 4 times each week, sometimes more. This started only with 2019.16 or 2019.20, I am not certain when. But it sure didn't used to happen. Clearly there is a software problem with 2019.20 and hopefully it will be fixed soon.

jerrykham | July 21, 2019

We have a Model S and a Model 3. The deceleration for a "phantom menace" happens daily to me (in the S) and also to my wife (in the 3). It did it a lot in her 3 on a recent 7 day trip from the SF Bay area to the Seattle area as well so it is not just the SF bay area roads. Honestly it is worst when in the "express lane" (what used to be the carpool lane, but then the politicians wanted money for it). For example the express lane going 40 MPH and the lane next to it going only 15 MPH. Watch out under those conditions! The "phantom menace" deceleration happens about 5 to 6 times on my 10 mile use of the express lane when that is going on. When you are in the normal lane and both lanes are running smoothly at similar speeds it seems to happen mostly only when passing a large vehicle like a truck or van and is much more rate. But yes, it is easy to reproduce when your lane is going 20+ MPH faster than the lane next to you. It is a reminder to keep very alert!

Stiction | July 22, 2019

Glad I have 2015 AP1...hasn't been spastic in ages ;)

Shesmyne2 | July 22, 2019

Yep. Has happened to me & sadly it makes me scold her :-(. My first look is in the rear view!
@murphyS- thanks for that. I’ve always hovered over the brake when in CC or now TACC
but I’ll have to change my habit.

Still Grinning ;-)