Fails to stop or hold position on a slope

[JohnHind]

In my first day with my brand new Model Y I ran into some really horrible behavior to do with Stopping Mode: Hold on a hill. I'll come back to that, but I have today done some more experiments and have a better understanding of what is going on and how to manage it, so I'll talk about that first. Note this is not FSD or even Autopilot, just old fashioned human driving.
My garage sits at the top of a steeply sloping drive with a sharp right-hand curve at the bottom. The slope is between 15 and 20 degrees. I have found, both when facing up hill and down hill and with Stopping Mode: Hold either with or without Off-Road Assist, that the vehicle will roll down hill with both peddles released. Most often this happens when releasing the accelerator peddle with the vehicle already moving downhill (drive engaged in that direction). However occasionally with the vehicle stopped, after engaging Drive or Reverse and releasing the brake peddle (accelerator also released), it will immediately start rolling down hill. It does not seem to matter if the drive direction is up hill or down hill, the vehicle still moves down hill. Problem is the car will not let you use the brake and accelerator peddles simultaneously as you would in a traditional car to start on a hill.
Hence the horrible situation on the first day. My drive has a sharp turn to the right at the bottom of the hill with a low wall to the left and in front. Trying to get to a position flat enough for the parking brake warning not to nag, I had driven forward and down hill until the front of the car was approaching the wall ahead. Every time I tried to reverse out of this position the car lurched forward closer to the wall! This could easily have become an irrecoverable situation! In fact I caught this just in time and was able to drive out forward turning to the right, but with literally about 2cm clearance!

 

[mongo]

In my first day with my brand new Model Y I ran into some really horrible behavior to do with Stopping Mode: Hold on a hill. I'll come back to that, but I have today done some more experiments and have a better understanding of what is going on and how to manage it, so I'll talk about that first. Note this is not FSD or even Autopilot, just old fashioned human driving.
My garage sits at the top of a steeply sloping drive with a sharp right-hand curve at the bottom. The slope is between 15 and 20 degrees. I have found, both when facing up hill and down hill and with Stopping Mode: Hold either with or without Off-Road Assist, that the vehicle will roll down hill with both peddles released. Most often this happens when releasing the accelerator peddle with the vehicle already moving downhill (drive engaged in that direction). However occasionally with the vehicle stopped, after engaging Drive or Reverse and releasing the brake peddle (accelerator also released), it will immediately start rolling down hill. It does not seem to matter if the drive direction is up hill or down hill, the vehicle still moves down hill. Problem is the car will not let you use the brake and accelerator peddles simultaneously as you would in a traditional car to start on a hill.
Hence the horrible situation on the first day. My drive has a sharp turn to the right at the bottom of the hill with a low wall to the left and in front. Trying to get to a position flat enough for the parking brake warning not to nag, I had driven forward and down hill until the front of the car was approaching the wall ahead. Every time I tried to reverse out of this position the car lurched forward closer to the wall! This could easily have become an irrecoverable situation! In fact I caught this just in time and was able to drive out forward turning to the right, but with literally about 2cm clearance!

Is it getting into Vehicle Hold mode?
Model Y Owner's Manual | Tesla

Might still have some roll when first applying the accelerator.
Also, the new blended regen/ brake feature may help, it needs to be selected in the options if/ when you get that update.

 

[Grabthar]

Hold works reliably and quite well for me, even on hills. It sounds like you may need a service call.

 

[Oreodriver]

Hopefully this can be sorted out for you! I find my Y on very steep hills much easier to control because it operates exactly the same as if on a flat surface no rolling back, no delay in acceleration. I have mine set to ‘hold’ for stopping mode & I hardly ever use the actual brake even on very steep grades. Just using 1 pedal like a dimmer switch for fast/slow. Releasing the pedal the car does not roll away like a gas car.
What you are describing is terrifying.

 

[railroader1988]

try creep mode..

 

[jcanoe]

With Creep mode driving you would need to press firmly on the brake pedal to engage Brake Hold while stopped such as at a stop light. To release Brake Hold mode simply press the accelerator or tap the brake pedal to begin moving. (I never use Hold mode driving as I much prefer Creep mode when I drive into my home garage. My right foot is always on the brake pedal so I can inch forward inside the garage to the correct parking position inside the garage (leaving ~2 ft in front of and ~ 2 ft. behind my Model Y.)

 

[JohnHind]

Creep mode is completely useless. When reversing up hill into the garage, there seems to be no resistance to rolling forward down hill as soon as the brake is released. At least in hold mode it holds most of the time! I took it to a Tesla Service Center (nearly 80 miles away). They could not duplicate the problem as there was no hill steep enough nearby, but they claimed to have fixed it by adjustment and loading new firmware. It may be a little better, but still does not hold reliably on my driveway. With practice and clearing out the garage so there is more clearance, I now feel fairly confident reversing in to the garage, but I still have to use the brake peddle to maneuver with sufficient precision.

 

[mongo]

Creep mode is completely useless. When reversing up hill into the garage, there seems to be no resistance to rolling forward down hill as soon as the brake is released. At least in hold mode it holds most of the time! I took it to a Tesla Service Center (nearly 80 miles away). They could not duplicate the problem as there was no hill steep enough nearby, but they claimed to have fixed it by adjustment and loading new firmware. It may be a little better, but still does not hold reliably on my driveway. With practice and clearing out the garage so there is more clearance, I now feel fairly confident reversing in to the garage, but I still have to use the brake peddle to maneuver with sufficient precision.

Yeah, manual calls that out, similar to an automatic transmission.

In some situations, such as on a steep hill or driveway, you may need to press the accelerator pedal to continue moving or to prevent Model Y from moving in the opposite direction.

 

[JohnHind]

Yeah, manual calls that out, similar to an automatic transmission.

Difference is that standard automatic transmission will let you ride the brake. The Tesla complains if you press both peddles at once and ignores the accelerator. This means you have to release the brake and only then can you press the accelerator leaving time for it to start rolling down hill even if that is against the selected drive direction. I really do not understand why hold is a problem for Tesla - it has full control of the brake and plenty of torque available in the motor, plus it must have wheel rotation sensors for the anti-lock so it ought to be straight forward to adapt torque to slope. In my view, regardless of mode, the car should never move against the selected drive direction and in Hold mode, the stopping distance on releasing the accelerator should be the same regardless of slope or the state of charge of the battery!

 

[mongo]

Difference is that standard automatic transmission will let you ride the brake. The Tesla complains if you press both peddles at once and ignores the accelerator. This means you have to release the brake and only then can you press the accelerator leaving time for it to start rolling down hill even if that is against the selected drive direction. I really do not understand why hold is a problem for Tesla - it has full control of the brake and plenty of torque available in the motor, plus it must have wheel rotation sensors for the anti-lock so it ought to be straight forward to adapt torque to slope. In my view, regardless of mode, the car should never move against the selected drive direction and in Hold mode, the stopping distance on releasing the accelerator should be the same regardless of slope or the state of charge of the battery!

I grew up driving manual transmission vehicles, but I know what you mean about two foot automatic driving where you throttle up before brake release.

The issue with using wheel speed sensors is that they only tell you speed, not direction. The new PM motors have encoders which give speed and direction, but the older AC induction don't.
So on some cars they could implement a pure motor hold, but not all.