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Autopilot / tacc freaks out at the same exact spot regardless of condition

So this is a bit weird, but I noticed that without fail, the tacc/autopilot always applies the brakes as it approaches a certain spot on the fwy.

No matter if it's day time, night time, clear day, cloudy day, cars or no cars, it always releases the accelerator and begin full regen braking until I press the accelerator to override it. It's smooth pavement, properly painted/marked, no recent construction.

Anyone have ideas regards to this logic? Probbaly happened close to 10 times already lol
 
Assuming that the lines and other lane markers are correct as you stated, the 1st thing that comes to my mind is something being picked up on the radar. It's even possible a nearby university or airport is causing feedback in the radar receiver and that causes the computer to want to slow down. I've identified an area of freeway that causes the camera to loose the lanes, but that is an optical issue (left right tracking) not a radar issue (speed distance etc).
 

ecarfan

Well-Known Member
Moderator
the tacc/autopilot always applies the brakes as it approaches a certain spot on the fwy... No matter if it's day time, night time, clear day, cloudy day, cars or no cars, it always releases the accelerator and begin full regen braking
By "full regen braking" do you mean that it feels like if you completely took your foot off the "go pedal" but did not apply pressure to the brake pedal?

Or do you mean it feels like if you moved your right foot from the go pedal to the brake pedal and applied pressure to the brake pedal. Not the same thing as what I describe just above.
 

Todd Burch

12-Year Member
Nov 3, 2009
8,495
37,846
Smithfield, VA
Could be some sort of radar interference as some have suggested...but I think it's more likely to be that there's some issue with the map tile that Tesla uses for autopilot in that area. For instance, maybe something is strange with their tile and the car starts to think there's a very sharp turn coming up--just for an instant.

Either way, I'd report it to Tesla, giving the GPS coordinates (you can get those from Google Maps I believe).
 
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thecloud

As rhythm raced inside, the ship came alive
Nov 24, 2014
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Sunnyvale, CA
Are you in the right lane? Is there an exit or lane split coming up where two separate marked paths from your position are possible?

I have a similar experience, going northbound on highway 85, as I'm coming up on the second El Camino exit (westbound) in Sunnyvale. I want to keep going in that lane and don't want to take the exit, but the car always cuts off acceleration abruptly at that point, as if I had completely taken my foot off the accelerator. Regen braking kicks in immediately and the brake lights come on (but AP is still on). I'm learning to keep my foot hovering over the accelerator to override it, or to just turn AP off before I get to that spot. Presumably AP is erring on the side of caution and preparing itself to take the exit, which would in fact require a much slower speed. However it doesn't turn the wheel in the direction of the exit, so perhaps the whole lane looks like an exit ramp.

Haven't noticed this issue anywhere else. Overall, AP performs beautifully and it's a joy to use on long trips.

Elsewhere on the forums, someone posted about an instance where AP always switches off at the southbound 405 flyover next to John Wayne Airport in Orange County. That could indeed be radar interference.
 
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thecloud

As rhythm raced inside, the ship came alive
Nov 24, 2014
1,780
1,657
Sunnyvale, CA
I have a similar experience, going northbound on highway 85, as I'm coming up on the second El Camino exit (westbound) in Sunnyvale.
Well, it seems all I had to do was post about it, and the problem went away. Tonight I had AP enabled and was approaching the same underpass/exit where the car would normally cut acceleration. Except this time, the issue didn't reproduce.

Will get the GPS coordinates to report it, if it happens again; that's a good suggestion.
 

NikeWings

Active Member
Apr 7, 2016
2,117
2,848
California
So this is a bit weird, but I noticed that without fail, the tacc/autopilot always applies the brakes as it approaches a certain spot on the fwy.

No matter if it's day time, night time, clear day, cloudy day, cars or no cars, it always releases the accelerator and begin full regen braking until I press the accelerator to override it. It's smooth pavement, properly painted/marked, no recent construction.

Anyone have ideas regards to this logic? Probbaly happened close to 10 times already lol

Where is it? If I'm nearby, then I'll try it from my car and see what happens.
 

andrewket

Well-Known Member
Dec 20, 2012
5,704
1,543
I've seen this occur on overpasses when the road below is a slower, secondary road. I believe the issue is the car's software is incorrectly determing its position as being on the secondary road, which causes the car to think the speed limit has changed. Tesla has a +5 limit for AP on secondary roads, so TACC begins to brake. Get a bit further down the road and the correct, faster limit is reinstated. It freaked me out a bit the first time it happened. Had there been a car following me closely they would have not expected me to brake hard as there was no traffic and I was in an express lane (which may have contributed to the incorrect position interpretation).
 
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