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Discussion Starter · #1 ·
I don’t have the courage to do so myself so I’m asking here...

what would happen, if anything, if the engine start stop button is pressed while the vehicle is driving?
 

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2019 Ascent Limited
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One long press of 3 seconds or 3 presses in quick succession will stop the engine while you are driving.

Page 323 in the 2019 Owner's Manual.

Not recommended...
 

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Discussion Starter · #3 ·
One long press of 3 seconds or 3 presses in quick succession will stop the engine while you are driving.

Page 323 in the 2019 Owner's Manual.

Not recommended...
Thanks. I was in the passenger seat at the time just wondering. I don’t think I’d be able to even convince myself to press it once much less 3x or a long press.
So what happens when the engine turns off...do you come to a screeching halt?
 

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In many modern vehicles, most buttons and switches are no longer hardwired directly to the components they operate. Rather, they act as inputs to an ECU (Electronic Control Unit). The ECU is a reliable, sophisticated computer that is programmed to control operations for the vehicle. Vehicles now often have several interconnected ECUs, for example, an Engine Control Module (ECM), Powertrain Control Module (PCM), Transmission Control Module (TCM), Brake Control Module (BCM), Central Control Module (CCM), etc. Most of the vehicle's critical components and operations are monitored and controlled by an ECU.

So when you press the engine start/stop button, an ECU senses the input. Not only can it sense the button, but it can also sense how long you hold it and/or how many times you press it. The ECU then decides which operation to perform based upon other factors such as if the engine is currently running or not and which mode the vehicle is currently in. The ECU receives inputs from many other sensors in the vehicle, so it knows the status of the vehicle at any given time and can make decisions based upon these factors. For a theoretical example, if you press the engine start/stop button when the vehicle is off, the ECU checks the status of the engine, if it determines it's not running, it then checks for the presence of the key fob. If it finds it in close proximity it'll read the specific key code to see if it matches. If it does, it'll then activate the starter motor. When it senses that the engine is running it'll then automatically deactivate the starter motor and activate all the vehicle operations for driving. This is a simplistic example, it actually does much more, but you get the idea.

So if you're worried that you can perform an operation that can inadvertently damage the vehicle, rest assured that the ECU programming has been carefully designed and tested to prevent most unintentional operations. This is not to say a driver cannot cause issues, but the ECU programming will likely prevent most problems before they occur.

Modern vehicles such as the Ascent are massively "smarter" than bygone era vehicles and they're getting more sophisticated with each redesign. I work for a company that, among other things, manufacturers automotive electronics. You'd be amazed at the pace of advancements in this field. The ECU hardware and software in your $35K Ascent is magnitudes more advanced than the billion-dollar Apollo electronics systems that flew men to the moon and back.
 

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ECU Design Team Meeting:

Ok, next on the agenda - How many times are we going to let these bozos press Start while they are driving before we decide they are doing it on purpose?
 

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ECU Design Team Meeting:

Ok, next on the agenda - How many times are we going to let these bozos press Start while they are driving before we decide they are doing it on purpose?
I used to design tool control software for semiconductor test equipment. This equipment had to be designed to be operated by almost anyone (unskilled labor) in order to remain competitive with China and Taiwan. These were large, million-dollar test systems testing expensive product, so equipment and product damage was not an option. And first and foremost was not letting anyone hurt themselves.

So, yes, on the agenda was how to prevent operators from destroying the test equipment and/or the product and/or themselves, no matter how bad they messed up. This was not easy, you had to account for so many variables and it was amazing the things even properly trained people would do wrong.

There were many companies that did this throughout the world. The company I worked for (IBM) owned many such machines manufactured all over the world. When it came to control software, US manufacturers could not be beaten. The worst software came, believe it or not, from Japan. They had some of the best electronics and mechanics, their hardware was almost artistic, but their control software was awful. No one could ever figure out why.

I see this in the Ascent's infotainment system. The hardware is fine but the software is terrible. If I had the source code, I could resolve most of the biggest problems in a few months. But a year after the Ascent has been released, the problems remain. Inexplicable. I'm not sure if it was programmed in Japan, but it has the same type of simplistic flaws and gross oversights I saw in Japanese tool control software.

Fortunately, the rest of the Ascent's control software is fine, and there's always hope that they'll fix and update the infotainment software.
 

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Discussion Starter · #7 ·
But have you tried it?! ?
That and throwing the shifter in reverse are just too much for me to even try!
 
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