[bina12834]

Mods feel free to move this to the proper section....I didn't really know which sub-forum to post this in....


I've been using my adaptive cruise control in stop and go traffic during my commute to and from work. I noticed that the last few seconds before it comes to complete stop there is this awful grinding noise coming from the front of the vehicle on the drivers side. I also noticed the same thing when it starts to take off from a stop. Does anyone else that has ACC notice this? Its not the brakes because in normal use they don't make a sound. It sounds like gears grinding or like what anti-lock breaks sound like when you slam on them.

 

[Pappa60]

I only notice it when the ACC has to adjust quickly when decelerating.

The manual talks about this noise. Says it is normal.

 

[bina12834]

Where is this mention in the manual? I didn't see anything in the ACC section.

 

[Tsuter]

Sounds like the abs module might be making some noise. If you've ever had traction control kick on when you're accelerating you'll get a noise that is similar to what you are describing, that's due to the abs module dumping valves and such to work the brakes, and the cruise is using the brakes as well and likely causing the noise. I wouldn't worry unless it gets noticeably worse. One thing you can try is a panic stop to see if the noises occur then as well, you would likely feel the pedal pulsing with it. But some noise is normal with the abs and traction controls system.

 

[bina12834]

Sounds like the abs module might be making some noise. If you've ever had traction control kick on when you're accelerating you'll get a noise that is similar to what you are describing, that's due to the abs module dumping valves and such to work the brakes, and the cruise is using the brakes as well and likely causing the noise. I wouldn't worry unless it gets noticeably worse. One thing you can try is a panic stop to see if the noises occur then as well, you would likely feel the pedal pulsing with it. But some noise is normal with the abs and traction controls system.

It does sound like the traction control noise. I wouldnt expect the ACC to sound any different than if i were in full control myself...

 

[Pappa60]

Where is this mention in the manual? I didn't see anything in the ACC section.

You are correct, it isn't in the ACC section. Guess I must've read it somewhere else. The manual does talk about ABS noises which Tsuter mentioned.

"ABS is activated during braking when the system detects one or more wheels begins to lock. Road conditions such as ice, snow, gravel, bumps, railroad tracks, loose debris, or panic stops may increase the likelihood of ABS activation(s).
You also may experience the following when ABS acti-
vates:
• The ABS motor noise (it may continue to run for a
short time after the stop).
• The clicking sound of solenoid valves."

 

[ultgar]

I picked up my Pacifica Limited last week and mine makes the same grinding sound when stopping while using ACC. I don't have any experience with other makes/models to know if this is normal for this system or just typical of Chrysler vehicles.
SD

 

[generaltso]

I don't have any experience with other makes/models to know if this is normal for this system or just typical of Chrysler vehicles.

My Cherokee doesn't make this noise. I assume it's the same (or very similar) system on the Pacifica.

 

[vinodam]

I have noticed the exact same grinding noise in stop and go traffic in my Pacifica with ACC engaged. I have also noticed the brake pedal feeling very hard if I override the system occasionally.

 

[PacificaLimited]

I know the noise you speak-of, but I think "grinding" is inaccurate as to what's really happening.

My understanding, is the system behaving normally. That's the sounds of the braking being applied by the system/mechanics. Think of the sounds when ABS kicks-in in most vehicles... it's the same sound. I know early-on (years-ago), I used to think there was something "wrong" when ABS kicked-in, but learned to accept and understand that it was functioning normally when I heard/felt it kick in.

To me, it sounds/feels exactly as I would expect if the same mechanical systems that control ABS were also involved in attenuating the brakes during ACC and collision avoidance.

 

[Damoncaravanman]

I hear the same noise and am not concerned.

 

[bina12834]

I know the noise you speak-of, but I think "grinding" is inaccurate as to what's really happening.

My understanding, is the system behaving normally. That's the sounds of the braking being applied by the system/mechanics. Think of the sounds when ABS kicks-in in most vehicles... it's the same sound. I know early-on (years-ago), I used to think there was something "wrong" when ABS kicked-in, but learned to accept and understand that it was functioning normally when I heard/felt it kick in.

To me, it sounds/feels exactly as I would expect if the same mechanical systems that control ABS were also involved in attenuating the brakes during ACC and collision avoidance.

Why would the ABS be coming on at 3 mph?

 

[PacificaLimited]

Why would the ABS be coming on at 3 mph?

I'm not saying the ABS is kicking-in... I am saying that the BRAKING system used for collision avoidance and ACC are most-likely the SAME system that controls/manipulates the brakes for ABS as well, hence the similar (identical) sound when activated. That's all.

 

[generaltso]

My Cherokee doesn't make this noise. I assume it's the same (or very similar) system on the Pacifica.

I take it back. Now that I'm listening for it, I've noticed that my Cherokee DOES make this noise too. I feel pretty confident that it's normal.

 

[haleme]

Bringing this back up, but we also have this noise in our 2017 when using ACC. This is not a noise that one has to listen for. When I turn it on in stop and go traffic, my wife asks what that noise is as it is very loud. It sounds and feels nothing like ABS stutter, more like rusty plates of metal scraping together. Once I disable, the noise goes away.

Comparing this to my Volvo XC60 with ACC, there is no noise and I can see the computer moving the brake pedal in both cars, so the function is similar. In both cars, I can also put my foot just over the brake pedal, disable the system and the brake pedal will be release by the ACC control module and hit my foot.

My concern is there may be an issue in the ACC brake control module and am having my dealer check it out tomorrow.

 

[matthewsjl]

No issue - ours does it too.

It would appear that the Pacifica implementation is using the ABS module to regulate the brake pressure vs the human way to do it via the pedal.

In an anti-lock situation, the ABS module regulates the pressure to stop wheel lock - it's this same sound that you hear when the Pacifica is using the brakes for ACC. There doesn't appear to be any pulsing of the pedal as in an anti-lock situation.

John.

 

[konnerbllb]

That makes sense, thanks for the explanation.

 

[Lightadjust2000]

Mine makes this noise in certain speed change situations, I think it's nothing to be concerned about other than a slight annoyance. my 2013 accord makes this same noise when braking quickly. To be honest, its a small quirk to live with given how amazing chrysler's implementation of ACC is. Some cars costing 2-3x more don't do it this well, meaning slow down and speed up, leave reasonable gaps, etc., etc. It's just one of the smoothest systems out there besides newer MB's.

Funny enough, my 2014 grand cherokee has ACC and does not make this noise.

 

[edvan12]

I have a 2018 Pacifica that had the same grinding sound when the ACC did a firm braking. I just had the ESS battery replaced and apparently the agency automatically does a software update because the grinding noise is gone. The mechanic said the separate ESS battery is no longer used because of the problems it has caused.