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post #1 of (permalink) Old 06-26-2016, 07:31 AM Thread Starter
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Adaptive cruise anomaly

Hello all,
Our 2016 Impala LTZ2 has now about 6500 miles on it. Recently we've experienced something VERY odd with the Adaptive cruise. We'll be going along just fine, and will come to a slower vehicle that causes the AC to slow the car. From what sounds like the drivers front corner of the car, is this quick "RRRRRRR" that sounds like you are running over a small piece of that serrated road like they put on the left shoulder. When it does it, the car slows a bit as if I tap the brake. It's a bit unnerving. Anyone else experience this? Perhaps it is something to do with the anti lock module but sure seems like it shouldn't do it. Plus it does it so infrequently, I would doubt taking it in, they would be able to replicate it.

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John

2016 2LTZ, Blue Velvet, Jet Black/Mojave, 20" wheels, sunroof, adaptive cruise, tech and convenience packages.
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post #2 of (permalink) Old 06-29-2016, 06:44 AM
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My first thought is that it's braking rather hard if you came up on the slower vehicle rather quickly and the front brakes tend to take more of that load than the rear. Just a quick stream of thought....!
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post #3 of (permalink) Old 06-29-2016, 07:18 AM Thread Starter
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Originally Posted by pitthr View Post
My first thought is that it's braking rather hard if you came up on the slower vehicle rather quickly and the front brakes tend to take more of that load than the rear. Just a quick stream of thought....!


No, it never does it during hard braking, just very light braking. Perhaps it's the antilock brake system pre-charging? I am guessing the anti lock brake system is what controls the braking for this system..

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post #4 of (permalink) Old 07-30-2016, 12:40 PM
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After several more trips since my last response, I have experienced the same effect as you mentioned in your initial post. While it doesn't happen every time we come upon a slower car, I have had the experience and I'm chalking it up to the operation of the systems involved. I do notice it more when the brakes seem to apply more abruptly.

I'm still amazed at how well it works and how easy it is to become lulled into a slower speed than what it's set at because you gradually come behind a slower moving vehicle. You have to be watching your own speed constantly.

Follow-up question: when the AC does slow the car, do the brake lights come on??
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post #5 of (permalink) Old 07-30-2016, 02:43 PM
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Welcome to ACC! I sure do miss it and what you experience is normal. That is just how ACC works. I would never trust the car though 100%. Any car for that matter when coming up on one a bit close. Hover that foot over the brake pedal just in case. Not sure about the brake lights. I would imagine so since the car will brake automatically if you come up to close and fast using ACC. I always put the setting at the farthest. I always wanted more then enough distance while using the feature. We had it in our 2013 Honda Accord Touring. We really wanted the ACC feature with our 2LTZ. Problem is. It comes in a package with the 20" wheels. I did not want those and feel the 19's are perfect for this car. I also like the look and style of the 19's on the 2LTZ much better.

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OEM Accessories: Splash guards, Wheel locks, Spoiler, Impala license plate frames and All weather floor mats with cargo mat
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post #6 of (permalink) Old 09-16-2016, 09:52 AM Thread Starter
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Wow, has this problem gotten worse. Have just under 12K on the car and the problem continues to get worse. It's about due for it's second oil change so I am going to have them look at it. Of course, it won't do it while they have it! Yesterday we were cruising along and came upon a slower moving car. The adaptive cruise applied the brakes and made this sound very loud and jerked the car as if I had jammed on the brakes for a split second. Scared the sh*t out of me. I sure hope they can figure it out. I hate intermittent issues..

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post #7 of (permalink) Old 09-16-2016, 11:57 AM
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Originally Posted by jonjonbear View Post
Wow, has this problem gotten worse. Have just under 12K on the car and the problem continues to get worse. It's about due for it's second oil change so I am going to have them look at it. Of course, it won't do it while they have it! Yesterday we were cruising along and came upon a slower moving car. The adaptive cruise applied the brakes and made this sound very loud and jerked the car as if I had jammed on the brakes for a split second. Scared the sh*t out of me. I sure hope they can figure it out. I hate intermittent issues..
Jonjonbear, I am having the exact same issue on my 2016 LTZ, and the same response from service that this is "normal." I have about 15,000 on mine now, and it is getting worse. I was told the ACC runs through the ABS (which that module is evidently in that front drivers side area). The vibration/grinding sound is annoying, but the hard braking is scary, and very disconcerting for my passengers and me. I contacted Chevrolet Consumer Hotline: 800-222-1020, and they have referred me to a new dealership, and are hopefully getting the regional folks and corporate engineers involved. For my next appointment, I am leaving my car (setting my trip odometer), and expecting them to drive around as if they own the car (for several days if needed), and use the ACC nearly all the time (I do use it a lot, even on non-highway roads, mainly so I don't speed). It's done it going on the downslope of a hill, or anytime the system senses the car needs to slow down and applies the brakes. Like yours, it's not consistent, but is happening nearly 65% of the time that the ACC "brakes", now (when the car was brand new, it happened like once a week at most). I am very frustrated. As I said, I use my cruise control a lot, and really do like the "adaptive" part of it. But, to me this is a safety issue...I can't have my passengers and objects thrown forward unexpectedly, and I am afraid a following-too-closely person is going to plow into me at 70 miles per hour one of these days. I hope "they" can get to the bottom of this anomaly, because it is not definitely NOT normal! Please post if you get any resolution for further information.
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post #8 of (permalink) Old 09-19-2016, 07:08 AM
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I don't have ACC, just the standard front collision warning system.

Do you see a lot of "false reactions" with ACC? I get a ton of those rapid beep warnings for no reason at all, even on the least-sensitive setting.

I would imagine a false reaction with ACC could be quite dangerous and cause a collision if your car jams on the brakes and someone is on the phone or otherwise not alert while following you.

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post #9 of (permalink) Old 09-19-2016, 07:44 AM
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ACC and our front collision use 2 completely different systems. ACC is radar based. Front collision is just a camera. If you are getting ALOT of false positives I would suggest cleaning the outside glass area where your rearview mirror is. I get a few here and there but not what I would describe as lots.

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post #10 of (permalink) Old 09-20-2016, 09:42 PM
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Mine is pretty sensitive...but it's not overly so. The ACC anomaly seems to be with its interaction with the ABS; a programming or relay timing issue. But, bignick2015, you are right...I have had it slam on the brakes numerous times (for only a 1 to 1.5 second "instant"), but it's jarring, and if I wasn't "holding the wheel," i.e., driving in a very relaxed posture, these brake-grabs could easily cause my hand to slip off the steering wheel and potentially cause me to lose control.

I didn't know the collision warning system used a different "system" to operate. See if what ICUBB suggests helps.
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post #11 of (permalink) Old 09-23-2016, 08:46 AM Thread Starter
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Quote:
Originally Posted by bignick2015 View Post
I don't have ACC, just the standard front collision warning system.

Do you see a lot of "false reactions" with ACC? I get a ton of those rapid beep warnings for no reason at all, even on the least-sensitive setting.

I would imagine a false reaction with ACC could be quite dangerous and cause a collision if your car jams on the brakes and someone is on the phone or otherwise not alert while following you.
Hi BigNick, Don't really get false reactions with the ACC, except one situation it doesn't like. If you are traveling in the left lane and the car in front of you turns into a left turnout, the car will brake abruptly, I guess thinking because the car you were following is decelerating quickly and the car hadn't yet realized the car you were following is in a different lane. Other than that, it's pretty well behaved except this horrible grabbing/grinding sound I get ever so often. I'm not so sure that the ACC and anti collision system are totally separate on the cars with ACC, because the collision avoidance system uses the ACC to stop the car. The CA system will brake the car even with the ACC off, specially if you have the foot on the gas. I think if you have your foot on the gas, the car thinks you have not seen the impending threat. There have been a couple of instances, where someone pulled out across in front of me and the car started beeping and flashing and applied the brakes before I even had time to take my foot off the gas. Pretty amazing. Another thing it did that surprised me, we were on a two lane highway and on the opposing side was a pickup truck parked on the shoulder. There were two surveyors standing there and one of them stepped quickly about half way across the opposing lane and our car started beeping and flashing. I didn't realize the Impala could detect pedestrians. It's not done it since, perhaps it was something else.

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post #12 of (permalink) Old 09-23-2016, 08:56 AM Thread Starter
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Originally Posted by TX2Stp View Post
Jonjonbear, I am having the exact same issue on my 2016 LTZ, and the same response from service that this is "normal." I have about 15,000 on mine now, and it is getting worse. I was told the ACC runs through the ABS (which that module is evidently in that front drivers side area). The vibration/grinding sound is annoying, but the hard braking is scary, and very disconcerting for my passengers and me. I contacted Chevrolet Consumer Hotline: 800-222-1020, and they have referred me to a new dealership, and are hopefully getting the regional folks and corporate engineers involved. For my next appointment, I am leaving my car (setting my trip odometer), and expecting them to drive around as if they own the car (for several days if needed), and use the ACC nearly all the time (I do use it a lot, even on non-highway roads, mainly so I don't speed). It's done it going on the downslope of a hill, or anytime the system senses the car needs to slow down and applies the brakes. Like yours, it's not consistent, but is happening nearly 65% of the time that the ACC "brakes", now (when the car was brand new, it happened like once a week at most). I am very frustrated. As I said, I use my cruise control a lot, and really do like the "adaptive" part of it. But, to me this is a safety issue...I can't have my passengers and objects thrown forward unexpectedly, and I am afraid a following-too-closely person is going to plow into me at 70 miles per hour one of these days. I hope "they" can get to the bottom of this anomaly, because it is not definitely NOT normal! Please post if you get any resolution for further information.
Hi TX2, I am going to take the car in for it's second oil change on Monday and talk to them about it. Oddly, since it had that big event, it's only had one tiny one so the chance of it doing it for them if I left it, is unlikely. I am going to show them your post, and perhaps they can at least document it, and perhaps contact their corporate folks to see if they know something. Perhaps a software update would fix it. I'm at just a bit over 11K now.

2016 2LTZ, Blue Velvet, Jet Black/Mojave, 20" wheels, sunroof, adaptive cruise, tech and convenience packages.
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post #13 of (permalink) Old 03-15-2017, 12:07 PM
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mine does not do that, but ive used it like 3 times, and my lane beeping thing is turned off too since all it does is beep.

Now if i could figure out how to get the red brake flash on the windshild and beeps to stop i might like this car.... BEEEP BEEEEP BEEEP.. like 100 times a day
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post #14 of (permalink) Old 03-15-2017, 02:04 PM
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Quote:
Originally Posted by KERR1 View Post
mine does not do that, but ive used it like 3 times, and my lane beeping thing is turned off too since all it does is beep.

Now if i could figure out how to get the red brake flash on the windshild and beeps to stop i might like this car.... BEEEP BEEEEP BEEEP.. like 100 times a day
Not sure if it exactly the same for models with the Adaptive Cruise Control as I do not have that option, but I do have Forward Collision Alert and that is the red flashing and beeping. To disable that click on the button shown in this picture until it turns to off. Again I don't know if you can turn it off on AAC models but worth a look.
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post #15 of (permalink) Old 03-16-2017, 04:55 AM Thread Starter
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Nope. On the adaptive cruise models, you can't turn it off.

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Originally Posted by ICUBB View Post
Not sure if it exactly the same for models with the Adaptive Cruise Control as I do not have that option, but I do have Forward Collision Alert and that is the red flashing and beeping. To disable that click on the button shown in this picture until it turns to off. Again I don't know if you can turn it off on AAC models but worth a look.
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