# ABS self check... why?



## neirfin (Oct 18, 2012)

so i understand that the cruze does an ABS check at about 12 mph, making a super sweet grinding/crunching noise, but does anyone know why, or what is happening during the check? what makes the noise, and why does it happen every time you get up to 12 mph?


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## Patman (May 7, 2011)

This question has been asked before: Why IDK but here is a previous thread:
*Startup Grinding Noise (Normal - It's the ABS Self Check)*

I agree this thread was not very informative but I tried to do some Google searches but it is common among all ABS systems on most all cars. It is just a system check to make sure all works well. Kind a like roll call and if something does not respond correctly, it lets you know: need I say more. With electronics and stuff sometimes that is just how it works.


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## iKermit (Dec 13, 2010)

I don't know but by all means...grind away and make sure I can brake


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## Robby (Mar 1, 2013)

You are hearing the ABS unit cycle its pump. If you look at the unit you will notice a small electric motor bolted to it.
That is the pump motor.
The unit operates on the order of approximatly 3000 psi........you are hearing it 'pressure up' to verify it is operating as designed.
If it cannot hit its target pressure within a predetermined time window (that one second or so thump you hear) a ABS fail light will set and the system reverts to non-ABS function......the brakes will apply normally but the system is incapable of automatically pumping the brakes (through pressure cycling).

As far as the target test speed......no particular reason I've ever read about.

Rob


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## jblackburn (Apr 14, 2012)

It pulses the solenoids in the ABS pump which activates each brake. 

All cars do it. Some just not as loud. Actually, after I have heard the Cruze do it for so long, I went back and heard my Volvo do it as well.


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## SavetheManuals! (Aug 14, 2014)

Ah that makes sense, I was curious as well, especially since the noise/test still occurs even when the car is off and rolling (albeit with the power on just engine off, not rolling with everything completely off) and even if the engine hadn't been started all day. Thanks for the info guys.


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## neirfin (Oct 18, 2012)

I've owned a few cars with abs and never heard it before. Maybe it was happening but just not loud like in the cruze... If I was designing the car I would've made it 10 mph, just to keep things even lol... 12 mph is a weird target.


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## iKermit (Dec 13, 2010)

neirfin said:


> I've owned a few cars with abs and never heard it before. Maybe it was happening but just not loud like in the cruze... If I was designing the car I would've made it 10 mph, just to keep things even lol... 12 mph is a weird target.


They may have factored in some numbers such as weight of the car to come up with that number. Doubt they just did it to be different lol. If they did though that is some good trolling.


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## jblackburn (Apr 14, 2012)

neirfin said:


> I've owned a few cars with abs and never heard it before. Maybe it was happening but just not loud like in the cruze... If I was designing the car I would've made it 10 mph, just to keep things even lol... 12 mph is a weird target.


Very, very quiet on the other cars I've had. Honda/Acuras used to be pretty loud though.


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## obermd (Mar 3, 2012)

neirfin said:


> I've owned a few cars with abs and never heard it before. Maybe it was happening but just not loud like in the cruze... If I was designing the car I would've made it 10 mph, just to keep things even lol... 12 mph is a weird target.


It's actually at 20 KPH (12.4 MPH).


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## Robby (Mar 1, 2013)

This one is IMO fairly quiet.

I think one could hear my 07 Commander self test from across the street, heh heh.

Possibly THE #1 question on that forum posted by a new owner.......I figured the folks at Jeep gotta go nuts trying to explain the self test.

Rob


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## neirfin (Oct 18, 2012)

When I heard it the first time during my test drive I thought it was busted... The salesperson told me it was normal but he didn't know what it was making the noise. Like I say it's the only car I have ever heard or felt it in, never heard it in the cobalt, camaro, mustang, or Tacoma, all had abs.


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