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Auto pilot malfunction ?

Today is was driving an a mojor highway in Michigan (I94). The speed limit was 70 and I had autopilot on cruising at 75. Three lane highway and I was in the center lane. No one in front of me in any lane and suddenly the car slammed on the breaks for no reason. The guy behind me almost rear ended me because of my sudden slowdown for no reason. I immediately took it off cruise control (autopilot) and went on my way. The car had slowed from 75 to 55 before I could disengage autopilot. I have never had this happen before. The only thing I can imagine is that there was a large overpass coming up and maybe the shadow on the road ahead of me fooled autopilot?
Any feedback or insights would be appreciated.

PS. I did continue to use autopilot the rest of the trip without incident.
 
Today is was driving an a mojor highway in Michigan (I94). The speed limit was 70 and I had autopilot on cruising at 75. Three lane highway and I was in the center lane. No one in front of me in any lane and suddenly the car slammed on the breaks for no reason. The guy behind me almost rear ended me because of my sudden slowdown for no reason. I immediately took it off cruise control (autopilot) and went on my way. The car had slowed from 75 to 55 before I could disengage autopilot. I have never had this happen before. The only thing I can imagine is that there was a large overpass coming up and maybe the shadow on the road ahead of me fooled autopilot?
Any feedback or insights would be appreciated.

PS. I did continue to use autopilot the rest of the trip without incident.
What happened? Elon was singing his theme song:
Promises, Promises.
Of course, it was YOUR fault!!!!!! heh ,heh.
 

bob_p

Active Member
Apr 5, 2012
3,738
2,947
This still happens periodically - no not as often as it did a year ago.

And, it's probably better for the software to over-react - than to risk it missing a real issue and not braking.

We've found this happens for two reasons:
  1. Speed limit data is incorrect and has a speed limit below the AutoSteer threshold. This is usually in areas of recent construction where the speed limit database hasn't been updated after the road changes have been completed. The speed limit database released last summer still has many areas with missing or incorrect speed limit data, which causes problems with AutoSteer when the speed limit database isn't showing the correct highway speed.
  2. The sensors believe there MAY be an object in the roadway ahead. This usually occurs when there is a heavy shadow or you hit a transition in the color of the roadway going from light to dark and then back to light again.
We treat AutoSteer as a student driver - and while it works most of the time (used it for most of the driving on a road trip last week), it still makes a few mistakes, so you need to be ready to take over control - at any time.
 
Today is was driving an a mojor highway in Michigan (I94). The speed limit was 70 and I had autopilot on cruising at 75. Three lane highway and I was in the center lane. No one in front of me in any lane and suddenly the car slammed on the breaks for no reason. The guy behind me almost rear ended me because of my sudden slowdown for no reason. I immediately took it off cruise control (autopilot) and went on my way. The car had slowed from 75 to 55 before I could disengage autopilot. I have never had this happen before. The only thing I can imagine is that there was a large overpass coming up and maybe the shadow on the road ahead of me fooled autopilot?
Any feedback or insights would be appreciated.

PS. I did continue to use autopilot the rest of the trip without incident.

Had the same issue a few weeks back and almost got rear ended by a semi. Only thing that saved the car was that I punched the gas.
 
Prior to the map updates, autopilot would slow drastically (but not dramatically), and in some cases for significant periods of time on Interstate 69 between US-231 and IN-37. This would happen in spite of the fact that there were no overpasses or other vehicles and the speed limit was still shown correctly in the IC. Service center said it was bad GPS data, but I haven't driven on the highway since the map updates to see if that is resolved. Regardless, it is important to know that you can override this with your foot on the gas. Much quicker to hit the gas and keep going than to reach for the autopilot lever to disengage.
 
I've had phantom braking like this a few times in AP recently at highway speed (75 mph). I did suspect it could be due to harsh sunlight. It doesn't do it very often, but I've now taken to switching AP off if someone is tailgating me before I get unlucky with the timing of this feature! I suspect this is a major reason why Tesla made a conscious decision to limit AEB in reducing speed by a maximum 25 mph rather than full-on braking to a standstill!

I also agree that nailing the accelerator is the best way to react when this happens.
 
Had this happen to me during a road trip on the highway and when this occurred I had noticed the speed limit sign on my dash went from 70 mph to 30 mph when the car decided to abruptly slow down while on autopilot. Had to take it off autopilot so I don't get rear ended. Waited until the speed limit on my dash turned back to 70 mph until I turned autopilot back on and didn't experience it for the rest of the drive.
 
Crazy thing about my experience is that the logs didn’t show the brake had activated. The guy at the SC said he saw where I hit the accelerator to 100% but no brake or errors shown. Since this was their loaner I called them immediately so they knew it was happening. I also figured if I reported it and it happened again and actually caused an accident maybe my insurance wouldn’t have to pick up the bill.
 
Crazy thing about my experience is that the logs didn’t show the brake had activated. The guy at the SC said he saw where I hit the accelerator to 100% but no brake or errors shown. Since this was their loaner I called them immediately so they knew it was happening. I also figured if I reported it and it happened again and actually caused an accident maybe my insurance wouldn’t have to pick up the bill.

THIS response scares the crap out of me. What you are saying is that the car can brake suddenly
and show nothing in the logs. If you had been rear-ended, the blame would be directly
placed at your feet because the car "obviously" didn't do anything.

Those logs *will* be used against you very publicly by Tesla if they think you are maligning
them - and you seem to have shown that those logs are not infallible.
 

DCGOO

Active Member
Supporting Member
Nov 24, 2015
2,058
1,352
Indianapolis, IN
Prior to the map updates, autopilot would slow drastically (but not dramatically), and in some cases for significant periods of time on Interstate 69 between US-231 and IN-37. This would happen in spite of the fact that there were no overpasses or other vehicles and the speed limit was still shown correctly in the IC. Service center said it was bad GPS data, but I haven't driven on the highway since the map updates to see if that is resolved. Regardless, it is important to know that you can override this with your foot on the gas. Much quicker to hit the gas and keep going than to reach for the autopilot lever to disengage.

It is probably fixed with the map update. I know the map update fixed the problems with the newer bridges and highways in Louisville. The old Navigon map database was severely stale. Very refreshing to finally have good data in the Louisville area. I suspect I-69 south is similar. If the Bloomington supercharger would come on line, I could make a round trip to Evansville <sigh>. Soon, very soon. Lol
 
It is probably fixed with the map update. I know the map update fixed the problems with the newer bridges and highways in Louisville. The old Navigon map database was severely stale. Very refreshing to finally have good data in the Louisville area. I suspect I-69 south is similar. If the Bloomington supercharger would come on line, I could make a round trip to Evansville <sigh>. Soon, very soon. Lol
Plenty of folks in the model 3 forum are seeing the same issue. My MX has AP1--that car has had no issue, but the model 3 with 2.5 has definitely seen this issue

PSA: CAREFUL--Autopilot sudden braking
 
THIS response scares the crap out of me. What you are saying is that the car can brake suddenly
and show nothing in the logs. If you had been rear-ended, the blame would be directly
placed at your feet because the car "obviously" didn't do anything.

Those logs *will* be used against you very publicly by Tesla if they think you are maligning
them - and you seem to have shown that those logs are not infallible.
I felt the same way by what they told me. They still don’t seem to really care the car did that. They said it must have been an overpass or shadow but there wasn’t anything around on this stretch of highway. I told them to google map the location and check for themselves.
 

ecarfan

Well-Known Member
Moderator
I’ve owned my X with EAP for almost a year and have used Auto Pilot for at least 7,000 miles of the 21K total on the car. I have had several instances of sudden deceleration when using Auto Pilot on freeways and highways at 65 to 70mph where the speed drops 5 to 10mph in about 1 second. I have not seen it drop by 15mph, but maybe that is because I am paying attention and take action by pressing on the accelerator to increase my speed.

I suspect that there are multiple causes for this behavior, and posts on this thread have described several of them. It’s probably not just one thing that causes the sudden deceleration.

That said, I don’t think it is as dangerous as some claim and I have yet to read a report of that Auto Pilot behavior resulting in a collision. Yes, tailgating drivers are a big problem and it is certainly possible that a sudden and unwarranted Auto Pilot deceleration could potentially result in a rear end collision. My personal driving style is that if I see someone tailgating me, whether I am on Auto Pilot or not, I try to get out of their way because they are driving stupidly and I don’t want to be around them. On a crowded highway I may not be able to change lanes immediately, but I do so at the earliest opportunity.

During my almost 50 years of driving experience I am continually astonished at how many drivers will tailgate on an uncrowded road where they have ample oppportunity to go around me. I estimate that at least a third of the drivers I see routinely follow the car ahead of them too closely. They seem to believe that they are protected by magical forces and have reaction times an order of magnitude faster than the mere mortals they share the road with. They are delusional. A state of mind which humans often have an affinity for.
 

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