2018 GMC Front Collision Alert not working

mgardner28 · January 31, 2019

I'm having the same issue. Just traded in a 2016 Sierra SLT 4X4 for a 2018 Sierra SLT 4X4 Z71. The 2016 front collision alert system worked perfectly. Almost no false alarms. Changing the distance also worked. I have not seen it work at all on the 2018. The green/yellow indicator does work indicating that it does see the vehicle in front of me. I've tried several of the same scenarios that would activate it on the 2016 and it has never activated on the 2018. I'm also seeing issues with the alert seat on the lane departure. The indicator light works and the steering wheel corrects, but the alert seat does not work when crossing the line to the right side. It works fine when crossing the line on the left side. The vibrators in the seat are working fine as they vibrate when backing up and get close to an object. I've only had the truck four days. I hate to take it in so soon to have something checked.

rrmccabe · January 31, 2019

Well I doubt you will get anywhere with it. All trucks seem to work different even if they are functioning. I finally gave up with dealer.

I do know it works as I had it save me a few months ago. Someone slammed on brakes a couple cars up and I was not paying attention and it stopped my truck without issues. I did not even see it coming.

Lane change thing is pretty much shut off all the time as it only works part of the time. I might use it if I do some highway driving late at night.

SS502 · January 31, 2019

42 minutes ago, rrmccabe said:

Well I doubt you will get anywhere with it. All trucks seem to work different even if they are functioning. I finally gave up with dealer.

I do know it works as I had it save me a few months ago. Someone slammed on brakes a couple cars up and I was not paying attention and it stopped my truck without issues. I did not even see it coming.

Lane change thing is pretty much shut off all the time as it only works part of the time. I might use it if I do some highway driving late at night.

X2

SS502 · January 31, 2019

2 hours ago, mgardner28 said:

I'm having the same issue. Just traded in a 2016 Sierra SLT 4X4 for a 2018 Sierra SLT 4X4 Z71. The 2016 front collision alert system worked perfectly. Almost no false alarms. Changing the distance also worked. I have not seen it work at all on the 2018. The green/yellow indicator does work indicating that it does see the vehicle in front of me. I've tried several of the same scenarios that would activate it on the 2016 and it has never activated on the 2018. I'm also seeing issues with the alert seat on the lane departure. The indicator light works and the steering wheel corrects, but the alert seat does not work when crossing the line to the right side. It works fine when crossing the line on the left side. The vibrators in the seat are working fine as they vibrate when backing up and get close to an object. I've only had the truck four days. I hate to take it in so soon to have something checked.

You’re describing almost word for word an earlier post of mine. Mine works (as defined by the dealership) and it has in fact gone off but it was damn near a crash...someone pulled in front of me from the right lane and it went off with the lights/seat and it felt like it started to brake but that could have been just my cat like reflexes LOL...I will only hope it works if ever needed. I will never rely on it and with my driving habits I hope to never be the reason it goes off.

BillK01 · January 31, 2019

18 minutes ago, SS502 said:

X2

X3

Seriously though, GM should be ashamed at how pathetic these safety features are in these trucks. My wife’s 2016 Toyota Highlander and my dad’s 2016 Lexus RX350 put my 2018 Denali to shame when it comes to the lane departure, parking sensors and forward crash assist features. I would have thought those sensors and cameras only came from a couple of suppliers but apparently GM has found the absolute cheapest supplier on the planet to source theirs from.

And don’t get me started on the horrible backup camera.

Edited January 31, 2019 by BillK01

rrmccabe · January 31, 2019

Well what is bad is if you watch the actual GM videos for frontal collision my truck does not work that way. Based on that you would be positive the truck is broke. I assume they have made some updates to the system since the video came out.

BlessedTexican · April 9, 2019

On 1/31/2019 at 5:06 AM, mgardner28 said:

I'm having the same issue. Just traded in a 2016 Sierra SLT 4X4 for a 2018 Sierra SLT 4X4 Z71. The 2016 front collision alert system worked perfectly. Almost no false alarms. Changing the distance also worked. I have not seen it work at all on the 2018. The green/yellow indicator does work indicating that it does see the vehicle in front of me. I've tried several of the same scenarios that would activate it on the 2016 and it has never activated on the 2018. I'm also seeing issues with the alert seat on the lane departure. The indicator light works and the steering wheel corrects, but the alert seat does not work when crossing the line to the right side. It works fine when crossing the line on the left side. The vibrators in the seat are working fine as they vibrate when backing up and get close to an object. I've only had the truck four days. I hate to take it in so soon to have something checked.

I am having many of the same issues you just described ... I traded a 2017 Sierra SLT where all the safety features worked exceptionally well, and I am now starting my 2nd week in a new 2018 Sierra Denali where about the only safety feature working consistantly is the lane departure on the right hand side ...not much of anything on the left hand side...no seat vibration on left hand side, no lane departure vibration on left hand side, no bell warning on left hand side, no frontal collison braking or light flash warnings, my green/ yellow indicator only shows green...very frustrated...I felt the same way you did about taking it in so soon after purchasing, but I now have close to 3k miles on it and I have tried the same scenarios that almost always woud trigger alerts in my 2017 SLT and I get hardly any alerts in the 2018 Denali. Dealer checked it out and said there were no codes to indicate a issue with any of the safety alert systems and said they would check it again when I come in for my first oil change to see if anything has changed...again, very frustrating!! It looks and sounds like to me GMC has changed something in the 2018 models .

Mike GMC · April 10, 2019

I'm sure you all have gone through the settings in the HMI and made sure all these alerts are turned on and set the way you want, but just in case, it might be worth a look. I found them when trying to turn off all the annoying nannies. I got a great deal on my truck and I love it, but I would not have ordered it with the all the electronic nannies. At least for me, they have proven easy enough to turn off.

BlessedTexican · April 11, 2019

3 hours ago, Mike GMC said:

I'm sure you all have gone through the settings in the HMI and made sure all these alerts are turned on and set the way you want, but just in case, it might be worth a look. I found them when trying to turn off all the annoying nannies. I got a great deal on my truck and I love it, but I would not have ordered it with the all the electronic nannies. At least for me, they have proven easy enough to turn off.

I love my new truck too...and I am aware of all the settings and how to set them, its just that I had been driving for the last two years a 2017 GMC Sierra SLT with exactly the same safety features that my 2018 Denali has and I had a great deal of confidence in the capablities of those safety features in the 2017 SLT because at least on my 2017 truck they all worked consistently as they were designed to work!!! I spend a lot of time on the road and I felt really good about the safety measures I had in the 2017... At the time of my trade I had no reason to believe that when I purchased the 2018 Denali that those same safety features would not perform as consistently as my 2017 did. It was not until my first long trip out last week in the new 2018 truck that I new something was amiss, that is when I joined this forum to see if any others were having the same issues that I was experiencing and it looks like there are a lot of others with the exact same problems that I am experiencing which leads me to question maybe some parts or programing has been downgraded, cheapened, or changed in the 2018's...very frustrating...still love my truck though! Just wish the safety measures I paid extra for, worked as they were designed on a consistent basis...

Justin101714 · April 15, 2019

I’m going with a bad haptic motor harness underneath the drivers seat.

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BlessedTexican · May 9, 2019

On 4/14/2019 at 10:12 PM, Justin101714 said:

I’m going with a bad haptic motor harness underneath the drivers seat.

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Appreciate the info... I am going to have the dealer check that when I go in for my next oil change. I now have had my truck for about 6-7 weeks and have pretty much accepted the fact that all the safety features on this truck are not going to work as well as the ones on my 2017...they all work, just not with any constistancy . Like last night, I was driving down the interstate and and there was a 18 wheeler (car hauler) a safe distance up ahead of me and my crusie was set on 75, he turned on his blinker to go around another truck and when he switched lanes the lights flashed on my windshield and my cruise was deactivated and my truck started to slow down...and I thought to myself ok it works...only problem was the truck was what i would consider way down the road from me .I'm just guessing here but maybe close to 100-150 yards or so, then I eventually go around him in a couple of minutes later and settle in behind another 18 wheeler, once again, way down the road from me and the alarm goes off again.... this makes the second time the alarm has gone off in the last two minutes or so for no apparent reason and I have been driving this truck the same way ,the same speed, down the same interstate , maintaining the same distance between me and the vehicles in from of me for the last six weeks without it going off a single time...I dont know if this has anything to do with it or not, but the car hauler truck was a double decker and it had a lot of lights all over, up and down, the sides of his trailer and the second 18 wheeler that activated my sensors had the standard tail lights on his flat bed trailer but he also had like a second row of lights about 2-3 ft above his normal tail lights on the back of his trailer ...I know this sound crazy, but it makes me think my sensors may have picked up on the additional lights...who knows...it is just strange to me that I have driven it for 6 weeks and nothing ...then last night it goes off twice within a couple of minutes of each other...just crazy !

gmr · August 15, 2019

2018 silverado high country, I just rear ended someone yesterday. I was going about 40, a car was beeping, checked my mirrors, looked around, looked forward and slam... no alert, no seat vibration, no beeps, no flashing lights except for the state police and ambulance. I'm not blaming my accident on a faulty system, just saying $60k and it didn't activate at all. Lane departure does not work either except for steering wheel feedback, no seat vibration or alert just wheel feedback, oh left side seat vibrate about 2% of the time. WTF

Edited August 15, 2019 by gmr