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Random sudden deceleration on AP.

jimbo69ny

Member
May 12, 2018
403
173
Ithaca NY
I just bought a brand new 2019 Raven long range X.

Love the car! Its amazing! I have a few issues though unfortunately. Mostly with details I found shortly after delivery. But this post isnt about that.

One issue I just discovered after 3 weeks of driving is that the car will suddenly decelerate while in AP sometimes. Nothing in the road, no obvious problems, no other cars or objects nearby, clear lines on the road, and suddenly the car will slam on its brakes for a second. But only for a second. Its really scary. Thankfully its only been me in the car when its happened.

I assume the car thinks it is seeing something to avoid but literally nothing is there. I read a post that someone said their car would suddenly decelerate because the database had old info of a previous work zone speed limit. Nothing like that for me although it also sucks that is a "thing" too.

Any advice?
 

VT_EE

Active Member
Apr 22, 2017
2,046
2,484
Maryland
This is what we call phantom braking. I'm now used to it. Most of the time it happens when there is either a bridge coming up or dark shadows on the road. I suspect the Tesla Vision system is mistaking the shadows for obstacles and then corrects itself. I have not had it slam the breaks on, but it does pull 10mph or so off quickly before recovering.
 
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r0xx0r

Member
Jul 9, 2016
437
335
CA
My advise is: feel the speed with your Tesla, hit the acceleration pedal according to its speed. It will help prevent phantom brakes.
 

K2500Z71

Member
Jul 17, 2019
209
142
Upstate NY
It’s called phantom braking and seems to have become worse for me after the last V9 software update. These issues seem to come and go with software updates.

I see it at times on I-86 (I’m in your area) and noticed the last time that the car mistakenly thinks the speed limit dropped to 40. It happens about 1/3 of the time on I-86 near Raymour & Flanagan... I wonder if there’s some sort of GPS interference that makes the car suddenly think it’s on one of the surface roads adjacent to the highway.

It is dangerous... I nearly got rear ended the other morning when it slammed on the brakes.
 

K2500Z71

Member
Jul 17, 2019
209
142
Upstate NY
The problem went away with the V10 update for me. AP seems to operate much more smoothly now... less abrupt acceleration and decelerations.

I do see an unusual behavior when merging on to I-86 now. It will merge into the right lane, then immediately initiate a lane change to the passing lane, stay there for 5-10 seconds then initiate a lane change back to the right lane.
 

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