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Discussion Starter #1 (Edited by Moderator)
So after less than 200kms on my Bolt I had a very scary issue today. While descending down a small hill I had a sudden jerk and it felt as if someone had rear-ended my car. Well that wasn't the case and in fact my car was just lurching forward uncontrollably. It took a lot of effort to bring it under control and had to jam the break to make it stop.

anyone else had a similar issue?
 

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One lurch? Many lurches like a bucking broncho? Where you in D? L?

Any error messages?
 

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Chevy Volt disables regen when the road surface is irregular. When this happens unexpectedly, it feels like the car is lunging forward ... even though it is not. Does the Bolt also disable regen when going on rough roads? If so, that could explain what you experienced.
 

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Agree it's likely the regen kicking out. Scary feeling but not actually a safety issue. The mechanical brakes will bring you to a stop. Having experienced it, you feel as if you're lurching forward when in fact you're simply not decelerating. On the Bolt EV the feeling may be more intense than on the Volt because regen is stronger.

In any case, it was definitely NOT the transmission. One reason for thinking that it was regen is that the Bolt EV doesn't have a transmission in the ordinary sense. The motor drives the wheels through a single reduction gear. Nothing there that could mechanically create a problem like you're describing, though that doesn't rule out electrical issues or something else.
 

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Agree it's likely the regen kicking out. Scary feeling but not actually a safety issue. The mechanical brakes will bring you to a stop. Having experienced it, you feel as if you're lurching forward when in fact you're simply not decelerating. On the Bolt EV the feeling may be more intense than on the Volt because regen is stronger.

In any case, it was definitely NOT the transmission. One reason for thinking that it was regen is that the Bolt EV doesn't have a transmission in the ordinary sense. The motor drives the wheels through a single reduction gear. Nothing there that could mechanically create a problem like you're describing, though that doesn't rule out electrical issues or something else.
That used to happen in my Spark EV and now my Volt. When over rough surfaces and decelerating under regen, the TC sometimes kicks in as the tires skip and the regen cuts out. It's a weird sensation. Somewhat like ALB.
 

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I also experienced this once on my Volt when coming to a stop. The road was a bit rough, and all of a sudden my car's breaking seems to have stopped and the car sprung forward. I did see the traction-control light come on momentarily so I realized what was going on. Thankfully I started my breaking very early so still had plenty of time to react, but it was a strange experience.

Now that I am aware of this, I try to coast through rough sections when I can so I haven't experienced this since.
 

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If the 'TO' suffix of the original poster's handle suggests Toronto, Ontario, it's quite likely that patches of ice may have been responsible for sudden modulation of the regenerative braking action. The recent heavy rains have washed away most traces of road salt, and the ambient temperature was at freezing from 06:00 through 11:00.
 

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Happens to me all the time (regen cutting out while braking) while I'm pushing my volt hard, and more in L mode with worn tires. I mostly solved this by getting deep tread performance tires over the LLRs. I lose a few miles of EV range, but the car is much more surefooted now.
 

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OP, consider buying a dash cam (comes in handy during an accident) and try and replicate this...It would greatly help the dealer diagnosis; sounds like you're one of the first to report this issue...
 

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Without more details from the OP on drive mode (D, L, region paddle), one lurch or multiple lurches, road surface conditions (rain, ice, gravel, RR tracks, pothole), it's hard to know whether this is truly a problem, or the normal behavior when region is lost thereby surprising the OP.
 

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As disconcerting as it might be, it would be useful to try to recreate the event. That is how I first became aware of the issue others are describing about TC in the Volt. One of my regular driving routes had a downhill where the TC would often kick out (losing regen from L when going down a 10% grade is concerning). My solution... turn off TC. >:-o

Slowing down and anticipating the bump also helped.
 

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Interesting issues to deal with. Yes, I have dealt with them in our Volt too. It's 'ok' when you can plan for it, it's dangerous when you can't. Or at least you know what to expect. We have had several times where it felt like the brake pedal went all the way to the floor when TC was activating. Like LL - studded tires helped, but doesn't eliminate it.

While the result of not stopping fast is the same in our Trax and my truck, the brake pedal feeling was more disconcerting in the Volt (until you know why).
 
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