following distance

[gcharles]

My 2017 Model S following distance changes without input without touching the controls. The following video was taken while the car was stoped and I was not in contact with either the steering wheel or the stalk controls.

Has anyone else experienced this? I'm guessing the rotary switch is at at fault which is surprising given I may have adjusted the distance less than a couple of dozen times over the life of the vehicle. I would guess the position is binary encoded, explaining the instant jump from 1 to 5, so a problem with bit 2, if you are counting from bit 0.

 

[DerbyDave]

Does the change remain after the car starts driving again? At the same time as the changes, the car on the right changes to a truck. Is this reproducible at every stop? Also, the automated driving changes manual settings.

 

[gcharles]

The change never remains for very long. I have never seen it remain for more than a second. The issue occurs when there is traffic nearby or on an "empty" road. I don't believe the autonomous driving software changes the manual settings. The following distance is set by a mechanical rotary switch on on the end of a stalk on the Model S. The switch has hard limits - it will only turn to the minimum or maximum position and will not keep rotating, unlike the rotary wheels on the steering wheel. This means that a specific physical position corresponds to a specific manually set value. Can you provide a pointer to the documentation which covers the automated driving changes the manual settings?

 

[DerbyDave]

Autopilot speed and following distance restrictions:

"After launching with a maximum speed of 75 mph and a follow distance as low as three vehicle lengths, Tesla increased the maximum speed to 80 mph just two months later. The follow distance was also lowered to two vehicle lengths in the same update."

Tesla to increase maximum Autopilot speed beyond 80 mph

Tesla will issue a software update in the future to increase the maximum speed you can use while on Autopilot.

www.notateslaapp.com

 

[gcharles]

Autopilot speed and following distance restrictions:

"After launching with a maximum speed of 75 mph and a follow distance as low as three vehicle lengths, Tesla increased the maximum speed to 80 mph just two months later. The follow distance was also lowered to two vehicle lengths in the same update."

Tesla to increase maximum Autopilot speed beyond 80 mph

Tesla will issue a software update in the future to increase the maximum speed you can use while on Autopilot.

www.notateslaapp.com

This post states a fixed minimum setting is being applied. In the video I shared it is bouncing between 1 and 5. If the minimum was somehow being applied to the manual setting, which I still doubt, then the setting should never be 1 (and visible as 1 in the video) according to this article. In my case, I'm not running the FSD Beta and the car includes the radar sensor. I'm not convinced the issue shown in the video is the result of autopilot software.

 

[DerbyDave]

I agree. I was only showing that autonomous driving can change or override the manual follow distances set by the driver.

 

[gcharles]

Tesla came back and have proposed changing out the stalk. It's not clear that they have diagnosed the issue with any degree of confidence and are simply replacing the stalk as the most obvious next step. Note that this issue first appeared about 18 months ago (while still under warranty) but it took a while for the problem to be frequent enough to capture it - to capture the issue I had to video my screen while driving, so I have to have my phone setup and be able to predict when it would occur. Initially it would only flicker once every few weeks, so no practical to capture the behavior. Tesla wants to charge me ~$350 for replacing the stalk. We'll see how the discussions go over warranty coverage. My advice to others if you see this once and you are under warranty, report it while you are still under warranty so you have some evidence supporting the timing of the first failure. Reading between the lines on the response from their technical team they were unable to determine much from the car's logs even when I gave them pointers with a timestamp accurate to within a second or two of the car's sense of time. Given this, I suspect Tesla has no evidence of the issue they can trace. FYI, they only keep full logs for the past month.