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New AP Behaviour: autopilot canceled itself. Safety issue? Normal?


Apr 21, 2018
Toronto, ON, Canada
So I have driven my 2017 AP2.5 75D for more than half a year. It's the first time I saw this behaviour (and I updated to 2018.21.9 only a couple days ago):

I was driving on a stop-n-go expressway in the morning with good weather conditions with autopilot engaged (following distance 3). The car in front of me made a relatively rapid deceleration - nothing too panicking. AP detects the slowing down and applies brakes rather quickly. The brake paddle makes a shuddering/thump/pulsing sound (which I have heard quite often before during rapid slow down by AP, which I think is normal). However, what's different this time is that right after hearing that sound, the AP just canceled itself! At the time, the car was still moving slowly forward. I had to take over and apply brakes further. And when this happened, the car only made a normal AP cancellation sound, no warning sound/no warning texts.

I'm not sure this is a normal behaviour - but I doubt it. It's the first time I have seen this. It feels as if AP was applying a little bit too much brake force to the brake paddle that triggers the AP to cancel. I would consider this a safety issue as AP would just cancel without either human intervention or proper warning after it did that.


Jun 24, 2016
Columbus, OH
Please contact Tesla, and give them the exact (or as close to it) time, so they can pull the logs from your car and analyze it. Let us know what they determine the cause was. This is not normal.


Apr 21, 2018
Toronto, ON, Canada
I did call Tesla right after the incident and gave them the exact timestamp when this happened. They told me they couldn't see any thing in the log around that time (no driver override nor cancellation). He doesn't seem to be convinced that this is a bug but he told me he would submit a bug report for engineers anyways.

Jan Fiala

Jun 24, 2017
Happened to me today (first day on 21.9) as well. It seems to me, that AP mistakes the sudden brake pedal movement (by itself) as driver input.


Active Member
May 5, 2016
Bay Area
This happened to me once before, on 2018.12. It seems to happen when AP makes a sudden braking input and then changes its mind. The pedal seems to bounce so much that the second bounce disengages AP.

I reported it to my SC as well as customer service but didn't get a response back from either.


Active Member
Oct 29, 2016
This also happened to me for the first time on 2018.20 recently. Similar situation where AP applied hard brakes, the brake pedal shuddered a bit (as it often does in hard brake applications) and AP disengaged. It's only happened to me once in 18 months of ownership, though I've had several strong AP brake events.

I also thought it was weird and the brake pedal shattering must have confused the car to think I was touching it.

I'm glad others have brake pedal shuddering as I thought mine was faulty maybe.

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