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Discussion Starter #1
Auto trans in L, was going forward, down an ice-covered driveway with very close 6ft stone walls of both sides, inching along, "feathering" the brake pedal so not to lock the wheels and this damned Hill Assist keeps kicking in making the wheels lock, putting the truck into a slide. I had to keep cancelling it using the ✔ on the steering wheel controls. I made it without hitting the walls but it was really close.

The owners manual says of hill assist, "It will not activate if the vehicle is in a drive gear and facing downhill" but that did not hold true.

Question: is there a way to cancel this feature? I need it for nothing.

(if it's in the Owner's Manual, I can't find it)

TIA.

(y)
 

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2017 Chevy Colorado Z71 Extended Cab 4WD Summit White
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Here is the write up from GM about it in the Colorado:
Hill Start Assist (HSA)

Hill Start Assist (HSA) feature on the Colorado is designed to prevent the vehicle from rolling, either forward or rearward, during vehicle drive off. After the driver completely stops and holds the vehicle in a complete standstill on a grade, HSA will be automatically activated to hold brake pressure for 3 seconds when a driver shift their foot from brake to acceleration pedal. It will not activate if the Colorado is in a drive gear and facing downhill, or if the vehicle is facing uphill and in R (Reverse).
 

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on my 2019 the automatic hill start assist only activates if I have fully stopped. while going down hill while in drive (or some forward gear I guess) and I change to reverse.

like I daily back down out of my car port, down a slight hill, then K turn around so I can drive forward down my driveway but i can not turn sharp enough to clear the fence that runs down the driveway so I stop to backup in reverse. I first hit the brake and at full stop I put it in R and the automatic hill start assist activates, shows in DIC and then I take my foot off the brake and it pauses (system holding the brake on for me) about 2 seconds so it does not roll forward as I remove foot from brake and put on accelerator since I am trying to get it to backup by applying light throttle. but the brake is still on. then the hillstart disenguages and it starts backing up. you have to be sure not to over do the throttle or it will fly backward and hit something! like the garage door or house!
hill start assist is handy as the brake pedal in my zr2 is small and it is hard to put two feet on it, like try to slide right foot over a little off the brake and slide left foot on as right foot goes to throttle. if I had a big powered break pedal (double wide) it would allow you to get the left foot on the brake pedal without worrying about rolling forward. but it is too small of a pedal for two feet.

and you can not use a hand brake as there is none and the parking brake is a brain dead push on - push off one that is hard to feather for this.

so I find the hill start assist feature valuable. you just need to get use to it.


BUT....in your case, did you accidentally do a full stop and cause it to lock up and was really sliding on ice, not really stopped? but interpreted it as a full stop and locked them causing it to slide further? It should not turn hill start assist on in that case unless you go to reverse.

I could see that as a problem. but if you are just crawling slowly it should not activate unless you locked up the tires on the ice maybe it could do that but it should not as you are not shifting to reverse.


or are you using hill desent control? not the automatic hill start assist?

I think Hill Descent Control may modulate the brakes and could maybe cause issues on ice?
 

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Does hill assist activate in manual shift mode?
 

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a quick check of Camaro forums shows this as a possible solution to deactivating HSA. Use at your own risk though, it involves replacing the yaw sensor with one that only looks at lateral accelerations rather than longitudinal. I've no idea what this type of modification might do to your stability control or other functions of your truck.


hill start assist is handy as the brake pedal in my zr2 is small and it is hard to put two feet on it, like try to slide right foot over a little off the brake and slide left foot on as right foot goes to throttle. if I had a big powered break pedal (double wide) it would allow you to get the left foot on the brake pedal without worrying about rolling forward. but it is too small of a pedal for two feet.
Maybe I'm dense here, but why would you need two feet on the brake pedal? These brakes are some of the most heavily assisted brakes I've ever used. Even when towing or the couple times I've been off road with my truck, I've never had issues holding the truck back with one foot on the pedal. Left foot braking so I can go-kart the pedals and/or feather, sure! But two feet on the brake?
 

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For reference, from the Owner's Manual (2015): Hill assist works in Drive or Reverse. And nothing in this description would make me believe the MANUAL mode would disable it. Tires that are not rolling as you slide on ice probably confuse the system, and I wonder how the system "senses" a grade.

Hill Start Assist (HSA)
This vehicle has an HSA feature, which may be useful when the vehicle is stopped on a grade
sufficient enough to activate HSA.

This feature is designed to prevent the vehicle from rolling, either forward or rearward, during vehicle
drive off. After the driver completely stops and holds the vehicle in a complete standstill on a grade, HSA
will be automatically activated. During the transition period between when the driver releases the brake
pedal and starts to accelerate to drive off on a grade, HSA holds the braking pressure for a maximum of
two seconds to ensure that there is no rolling. The brakes will automatically release when the
accelerator pedal is applied within the two-second window. It will not
activate if the vehicle is in a drive
gear and facing downhill, or if the vehicle is facing uphill and in
R (Reverse).
 

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Per the 2015 Electrical, I suspect the LONGITUDINAL ACCELERATION input can really confuse things if the truck is in motion, but the wheels are locked up. Not a lot of detail in the electrical description.

The following inputs are used for hill hold start assist feature:
• Accelerator pedal position
• Brake switch
• Brake pressure
• Clutch switch, if equipped
• Engine torque
• Longitudinal acceleration
• Reverse gear information
• Vehicle speed
 

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Discussion Starter #9
Per the 2015 Electrical, I suspect the LONGITUDINAL ACCELERATION input can really confuse things if the truck is in motion, but the wheels are locked up. Not a lot of detail in the electrical description.

The following inputs are used for hill hold start assist feature:
• Accelerator pedal position
• Brake switch
• Brake pressure
• Clutch switch, if equipped
• Engine torque
• Longitudinal acceleration
• Reverse gear information
• Vehicle speed
I'm sure you're on to something here. Keep in mind that right before this happened, I was backing up and going forward to position the truck just right to line it up with the center of the driveway. I may have totally confused the truck into engaging the hill assist.

I also failed to mention that I had the transfer case in 4↑ -- I just tried to recreate this scenario on a steep hill, albeit on dry pavement, and could not get it to happen again.

(y)
 

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I'm sure you're on to something here. Keep in mind that right before this happened, I was backing up and going forward to position the truck just right to line it up with the center of the driveway. I may have totally confused the truck into engaging the hill assist.

I also failed to mention that I had the transfer case in 4↑ -- I just tried to recreate this scenario on a steep hill, albeit on dry pavement, and could not get it to happen again.

(y)
If you find yourself needing to make a similar maneuver again, I would select 4WD Lo. Not that you need the lower gears, but with the lower gears, even if something goes off kilter, it all should happen at a lower speed and that may equate to better control.

Note, the manual refers to being in DRIVE and pointed DOWNHILL. What it means by drive is either D or the Manual (or whatever they call it in 2017.) Reverse is NOT a DRIVE gear in this nomenclature.
 

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HSA is handy for folks with one leg
 

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Arthur, do you have a Z71? Maybe you have the Hill descent feature, not sure if that turn on automatically or not, i have an LT and does not have this feature.
You have to turn that on using a switch on the console for it to be active.

I'm sure you're on to something here. Keep in mind that right before this happened, I was backing up and going forward to position the truck just right to line it up with the center of the driveway. I may have totally confused the truck into engaging the hill assist.

I also failed to mention that I had the transfer case in 4↑ -- I just tried to recreate this scenario on a steep hill, albeit on dry pavement, and could not get it to happen again.

(y)
So, it came on because you were reversing and came to a complete stop then put it in drive to go forward up the hill. Makes sense now, as that is when it is supposed to activate.
 

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When it comes to issues that you cant replicate, then I for one would just ignore it. No one knows your truck better than you so Im sure what you stated happened but,sometimes with the massive amount of electronics we have in these vehicles, the computer gets stupid there for a moment.
In the 5 or so years of the 2nd Gens,this is the first Ive seen or heard of this situation so my guess is, you just had a little gremlin visit you for the moment. Just be glad he left and didnt leave anything behind.

 

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Discussion Starter #16
When it comes to issues that you cant replicate, then I for one would just ignore it. No one knows your truck better than you so Im sure what you stated happened but,sometimes with the massive amount of electronics we have in these vehicles, the computer gets stupid there for a moment.
In the 5 or so years of the 2nd Gens,this is the first Ive seen or heard of this situation so my guess is, you just had a little gremlin visit you for the moment. Just be glad he left and didnt leave anything behind.

You're right, Ant. This isn't the first gremlin I've encountered and it probably won't be the last.

Thanks all for the replies.

(y)
 

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Maybe try in neutral and just feather the brakes and coast down the hill. With your hand on the shifter you could slip into drive quickly if you felt it was necessary. Would the hill decent assist still activate?
 

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Her is a video about Hill Descent Assist. But if the issue is Hill Descent Assist, you just have to turn it off.
 
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