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OliverM5
03-23-2007, 03:07 PM
My 2002 Yukon brakes lose almost all power when brakes are suddenly applied over rough terrain - seems like ABS engages and the brakes become useless for a few seconds. Almost had a few bad accidents this way...
Anyone else have this problem? Is there a way to disable the ABS without pulling the fuse (dash lights up when fuse is pulled)?

plaster dave
03-23-2007, 03:42 PM
My 2002 Yukon brakes lose almost all power when brakes are suddenly applied over rough terrain - seems like ABS engages and the brakes become useless for a few seconds. Almost had a few bad accidents this way...
Anyone else have this problem? Is there a way to disable the ABS without pulling the fuse (dash lights up when fuse is pulled)?
You can pull the abs sensor on the wheel hubs but I would go to a dealer and have them looked at.

SOCALDETAIL1
03-23-2007, 03:47 PM
My 2002 Yukon brakes lose almost all power when brakes are suddenly applied over rough terrain - seems like ABS engages and the brakes become useless for a few seconds. Almost had a few bad accidents this way...
Anyone else have this problem? Is there a way to disable the ABS without pulling the fuse (dash lights up when fuse is pulled)?
Yea my 2000 silverado did the same.

Sleek-Jet
03-23-2007, 04:14 PM
That's why ABS sucks... I wish you could "de-select" it depending on conditions and terrain...

SOCALDETAIL1
03-23-2007, 04:31 PM
my 2000 & 2003 did that, all I got were lame answers from the dealer, and when I called GM in Michigan, they said, never heard of that problem, yea rite, and it isn't a good feeling when yer not feeling any brake !!!!:mad:
When I worked for GM the techs told me thats a little signal to let you know the ABS is working.;)

Outnumbered
03-23-2007, 05:58 PM
Yep, my 1998 2500 4x4 did that too. Actually almost got hit because of it once. Chevy ABS sux ass.

707dog
03-23-2007, 06:41 PM
doesnt it matter also if you have oversized wheels...?

BadKachina
03-23-2007, 07:09 PM
Anyone else have this problem? Is there a way to disable the ABS without pulling the fuse (dash lights up when fuse is pulled)?
You could unplug the sensors at the wheels in front and the diff in the rear, your brakes will still work. You'll probably have a check engine light on though.
doesnt it matter also if you have oversized wheels...?
It shouldn't as long as all the tires are the same size. It only senses differences in wheel speed.

upsman105
03-23-2007, 08:13 PM
[QUOTE=707dog;2461753]doesnt it matter also if you have oversized wheels...?[/QUOT[/I]
I was told this, with oversized wheels it throws the sensors off. Need to have the computer reprogrammed.

Screemy1
03-23-2007, 08:38 PM
my 95 dodge 3/4 ton does it too... since new... the washboard dirt roads shake so much it makes the brakes weak... I just slow down and plan for it.... kinda scary at first..

JAY4SPEED
03-23-2007, 09:00 PM
My 2002 Yukon brakes lose almost all power when brakes are suddenly applied over rough terrain - seems like ABS engages and the brakes become useless for a few seconds. Almost had a few bad accidents this way...
Anyone else have this problem? Is there a way to disable the ABS without pulling the fuse (dash lights up when fuse is pulled)?
Why disable a safety feature that your truck was designed with? If the ABS activates over rough terrain, its doing exactly what its designed to do. ABS does not and never will shorten stopping distances for vehicles. It just keeps you in control while your are braking (Retains steering while under braking) When the ABS activates, your supposed to just keep even pressure on the pedal and don't pump the brakes, the ABS module and ABS pump motor are doing all the work so you wont feel any feedback on the pedal and it will feel dead, but its working.... Does the ABS activate prematurely on smooth terrain? There are several things that can cause that. Do you have non stock size wheels on the truck? You may want to check with your dealer to see if your truck may be included in a campaign where the front wheel speed sensors have to be inspected for corrosion, those had premature ABS activation. If you feel like its not operating as its supposed to, get it checked out instead of disabling it, the life you save may be your own.
doesnt it matter also if you have oversized wheels...?
Yes, over sized wheels do throw ABS out of calibration.
You could unplug the sensors at the wheels in front and the diff in the rear, your brakes will still work. You'll probably have a check engine light on though.
It shouldn't as long as all the tires are the same size. It only senses differences in wheel speed.
Your only half correct. The wheel speed sensor do detect differences in wheel speed but, ABS is calibrated for a specific size tire and wheel. Change that combo and you change the way your ABS behaves.

BajaMike
03-23-2007, 09:24 PM
Why disable a safety feature that your truck was designed with? If the ABS activates over rough terrain, its doing exactly what its designed to do. ABS does not and never will shorten stopping distances for vehicles. It just keeps you in control while your are braking (Retains steering while under braking)
I agree.....if the road is that rough, slamming on the brakes would not stop you anyway. The brakes would lock up and you would loose control.
They are doing just what they are designed to do.:idea:
On a rough road, you should slow down and keep a much greater distance from things ahead of you, just like you should in rain, snow or ice.
At the high speed driving school at the San Bernardino Sheriffs Academy, they have police cars that you can turn the ABS on and off, to learn how to drive in a skid on the skid pad.
They also demonstrate how well anti-lock brakes work, by doing a panic stop with the left wheels on the wet skid pad and the right wheels on dry pavement.......with the ABS off, you spin out of control. With the ABS on, you stop nice and straight and in control.
:eek:
That driving school is a blast, by the way!

Kachina26
03-23-2007, 10:29 PM
I know there was a bulletin on my 2001 for a new brake controller due to abs activation over rough roads. Give me a little time to look it up. (gotta "borrow" a password). Perhaps Jay4speed could look it up.

OliverM5
03-23-2007, 10:31 PM
I know there was a bulletin on my 2001 for a new brake controller due to abs activation over rough roads. Give me a little time to look it up. (gotta "borrow" a password). Perhaps Jay4speed could look it up.
That would be great....

IMPATIENT 1
03-23-2007, 10:33 PM
Why disable a safety feature that your truck was designed with? If the ABS activates over rough terrain, its doing exactly what its designed to do. ABS does not and never will shorten stopping distances for vehicles. It just keeps you in control while your are braking (Retains steering while under braking) When the ABS activates, your supposed to just keep even pressure on the pedal and don't pump the brakes, the ABS module and ABS pump motor are doing all the work so you wont feel any feedback on the pedal and it will feel dead, but its working.... Does the ABS activate prematurely on smooth terrain? There are several things that can cause that. Do you have non stock size wheels on the truck? You may want to check with your dealer to see if your truck may be included in a campaign where the front wheel speed sensors have to be inspected for corrosion, those had premature ABS activation. If you feel like its not operating as its supposed to, get it checked out instead of disabling it, the life you save may be your own.
Yes, over sized wheels do throw ABS out of calibration.
Your only half correct. The wheel speed sensor do detect differences in wheel speed but, ABS is calibrated for a specific size tire and wheel. Change that combo and you change the way your ABS behaves.
i agree 100% too, your abs is working, just keep steady pressure on the pedal when that happens to ya;) the abs shortens stopping distance by alot compared to wheels locking up and grinding to a halt.

Kachina26
03-23-2007, 10:36 PM
i agree 100% too, your abs is working, just keep steady pressure on the pedal when that happens to ya;) the abs shortens stopping distance by alot compared to wheels locking up and grinding to a halt.
abs can actually increase stopping distance, the job of abs is to allow you to maintain control during heavy braking, to allow you to get around what you are braking so heavily for. We all know that you can't steer while skidding.

JAY4SPEED
03-24-2007, 09:23 AM
I know there was a bulletin on my 2001 for a new brake controller due to abs activation over rough roads. Give me a little time to look it up. (gotta "borrow" a password). Perhaps Jay4speed could look it up.
This is the only bulletin I found in SI that had to deal with premature ABS activation (assuming a 2001 Yukon w/ 4wd):
Subject: Antilock Brake (ABS) Activation at Low Speeds (Clean Wheel Speed Sensor Mounting Surface) #03-05-25-007C - (05/16/2006)
Models: 2002-2006 Cadillac Escalade, Escalade EXT
2003-2006 Cadillac Escalade ESV
1999-2006 Chevrolet Silverado
2001-2006 Chevrolet Suburban, Tahoe
2002-2006 Chevrolet Avalanche
2003-2006 Chevrolet Express
1999-2006 GMC Sierra
2001-2006 GMC Yukon, Yukon Denali, Yukon XL, Yukon Denali XL
2003-2006 GMC Savana
2003-2006 HUMMER H2
Thats the only one that seems close to what he's describing. The other bulletin with the EBCM faulty ground had codes involved and didn't mention premature ABS activation.
OliverM5, do you have an ABS light on all the time on the dash? When it happens is it under or over 5 mph?
I've seen cracked reluctor rings on the old school ABS systems cause premature ABS operation but haven't seen it in the newer sealed bearing style wheel speed sensors yet.
Jay

JAY4SPEED
03-24-2007, 09:31 AM
i agree 100% too, your abs is working, just keep steady pressure on the pedal when that happens to ya;) the abs shortens stopping distance by alot compared to wheels locking up and grinding to a halt.
abs can actually increase stopping distance, the job of abs is to allow you to maintain control during heavy braking, to allow you to get around what you are braking so heavily for. We all know that you can't steer while skidding.
Kachina 26, I had to read it twice but I understand what IMPATIENT 1 meant. He knows ABS doesn't shorten stopping distance in normal conditions, he's saying that compared to skidding out of control in adverse conditions, the ABS will stop in less distance.
My whole point is that some people have the MISconception that because their vehicle has ABS that they subconsciously can tailgate a little closer thinking their vehicle will stop in a shorter distance if it didn't have ABS (in dry normal conditions), which we all agree, isn't the case.

OliverM5
03-24-2007, 09:39 AM
OK....let's get this straight, I know what ABS does and what it feels like. I know it makes braking safer and helps stop the car faster and in a more controlled manner. What I am experiencing with my car is not what ABS is supposed to be doing....the brakes pretty much go DEAD when what I am describing happens....I'll be driving along and have to slam on my brakes, and if this happens over a rough spot of road, I hear the ABS motor activate and the brakes go dead for a few seconds...very dangerous

Kachina26
03-24-2007, 09:39 AM
Kachina 26, I had to read it twice but I understand what IMPATIENT 1 meant. He knows ABS doesn't shorten stopping distance in normal conditions, he's saying that compared to skidding out of control in adverse conditions, the ABS will stop in less distance.
My whole point is that some people have the MISconception that because their vehicle has ABS that they subconsciously can tailgate a little closer thinking their vehicle will stop in a shorter distance if it didn't have ABS (in dry normal conditions), which we all agree, isn't the case.
Cool, just so long as we're all on the same page. :D
Oh yeah, I was wrong about the bulletin. It was on my other GMC which was a 98. Sorry, I was having a senior moment there.
Oliver, I'm a little confused about your description of the problem. You say you lose all power when braking hard, what power are you talking about? Braking power? Does the pedal get hard to push? Mushy? Vibrate? Have you taken it in to the dealer for this?

squirt'nmyload
03-24-2007, 11:29 AM
Kachina 26, I had to read it twice but I understand what IMPATIENT 1 meant. He knows ABS doesn't shorten stopping distance in normal conditions, he's saying that compared to skidding out of control in adverse conditions, the ABS will stop in less distance.
My whole point is that some people have the MISconception that because their vehicle has ABS that they subconsciously can tailgate a little closer thinking their vehicle will stop in a shorter distance if it didn't have ABS (in dry normal conditions), which we all agree, isn't the case.
i had this happened on my 03 denali last sunday while driving on a dirt washboarded road.......it felt like i lost them for a couple seconds..f in scary cause boat was in tow....i let off and reapplied and they worked fine, but i did feel the abs kick in a couple times after that

JAY4SPEED
03-24-2007, 09:58 PM
OK....let's get this straight, I know what ABS does and what it feels like. I know it makes braking safer and helps stop the car faster and in a more controlled manner. What I am experiencing with my car is not what ABS is supposed to be doing....the brakes pretty much go DEAD when what I am describing happens....I'll be driving along and have to slam on my brakes, and if this happens over a rough spot of road, I hear the ABS motor activate and the brakes go dead for a few seconds...very dangerous
I understand what your saying now. The truck is doing what its supposed to do, not a premature ABS situation.
I can relate to how that is alarming when the pedal drops to the floor. The truck basically takes the control away from you and thats what is unnerving to some. But, keep in mind that the valving of the ABS can operate in milliseconds, cycle 100s of times a second and the ABS pump can put out extremely high pressure, more than you could ever generate with your foot on the pedal. So think of it this way, while your brake pedal goes to the floor, the abs pump motor hits the brakes harder than you ever could generate on your own and modulate it 100's of times a second to keep the wheel thats slipping from locking up. So in a way, the ABS does a better job at stopping that wheel than any pro race driver ever could.
I know its hard to put blind faith into a machine but when you understand what happens behind the scenes (under the vehicle) and how fast that system can react and how sophisticated it is, its a whole lot easier to keep the faith in the system.
I'd bet you'd feel a lot better if the pedal had feedback from the system working or if it just stiffened up while the ABS is operating. But, unfortunately, nothing much can be done about that, its just the way its designed. In fact my F150 does the same thing, but the only difference is that you can feel the pedal pump slighty from the ABS motor in the Ford, but it isn't much different than GMs setup.
Anyways, If you lived closer out my way, I'd take a look at it for you at no charge. If you feel something just isn't right about it, bring it in and have it checked out. Ask if they might have another vehicle of the same type and year to compare it to, to be sure that what your describing your truck is doing is in fact, abnormal. That would be the only way to be sure.
Good luck with it:)
Jay

JAY4SPEED
03-24-2007, 10:06 PM
i had this happened on my 03 denali last sunday while driving on a dirt washboarded road.......it felt like i lost them for a couple seconds..f in scary cause boat was in tow....i let off and reapplied and they worked fine, but i did feel the abs kick in a couple times after that
Correct! Thats how it feels when the ABS kicks in. If your truck has the Tow / Haul button on the gear shift lever, one of the things that is done when that mode is selected is to modify the ABS calibration to allow for more gross vehicle weight from towing to keep it from kicking on when it isn't supposed to and boost up the pressures when it is, as well as a ton of other cool stuff that goes on.
Jay

JAY4SPEED
03-24-2007, 10:11 PM
Cool, just so long as we're all on the same page. :D
Oh yeah, I was wrong about the bulletin. It was on my other GMC which was a 98. Sorry, I was having a senior moment there.
No sweat Bro :D
You still in the business? After 8 years at my current dealer and turning wrenches other places for 15 years, gaining my ASE and GM Master status and being 2 assesments away from being GM World Class, I'm just about at the point where I'm questioning why I still am.... LoL :D

OliverM5
03-24-2007, 10:37 PM
Correct! Thats how it feels when the ABS kicks in. If your truck has the Tow / Haul button on the gear shift lever, one of the things that is done when that mode is selected is to modify the ABS calibration to allow for more gross vehicle weight from towing to keep it from kicking on when it isn't supposed to and boost up the pressures when it is, as well as a ton of other cool stuff that goes on.
Jay
Jay, I appreciate your input, but ABS does not mean that the brakes should let go altogether if a bump is encountered in the road. My car literally will coast for 5-10 seconds WITHOUT any brake force at all if a bump in the road sets off the ABS during hard braking.

Wicky
03-25-2007, 09:24 AM
ABS SUCKS without a deactivation button!! BMW motorcycles have the ability to overide why can't GM?
I had a brand new 97 Dakota that I took out the first day I had it.
Attempted to climb a killer steep hill with it and couldn't make it over the top.
Started to back down and Focking A!!!!
Brakes immediately went to the floor and I was flying down the hill in reverse.
This was not fun. Pulled off a Starsky and Hutch at the bottom before going off a cliff.
My 99 GMC had some kind of short and the ABS drained the battery by not shutting off even with the keys out of the ignition. That sucked. Two days before a road trip.
Haven't had any issues with the 03 GMC. Haven't gone up any super steep hills yet either.
ABS sucks!! If you can't brake over washboard...why have brakes at all?
Ranting,
Wicky...Mow!!

squirt'nmyload
03-25-2007, 08:10 PM
Correct! Thats how it feels when the ABS kicks in. If your truck has the Tow / Haul button on the gear shift lever, one of the things that is done when that mode is selected is to modify the ABS calibration to allow for more gross vehicle weight from towing to keep it from kicking on when it isn't supposed to and boost up the pressures when it is, as well as a ton of other cool stuff that goes on.
Jay
i was using the tow/haul button at that time:)

Outnumbered
03-25-2007, 08:23 PM
Im going to side with Oliver on this one. Unless you have had this happen to you, you really don't know what he is talking about. Mine did it in a rough section of a private road we used to live on. It was a steep downhill and had a few pot holes. When we got our Dodge 2500 with ABS it DID NOT do this when driven over the same section. It will scare the shit out of you because it is like the bumps cause the ABS computer to get "confused" and you would bassically coast for about 10-15 feet with no brakes. This was hapening at under 20 MPH too so it is not like a 75 MPH panic stop. I had to do a 75 MPH panic brake when a focking cow ran in front of my Durango on the way to Mead one night. The ABS in the Dodge was amazing. Worked flawlessly and probably saved my ass.

dicudmore
03-25-2007, 09:39 PM
Jay, I appreciate your input, but ABS does not mean that the brakes should let go altogether if a bump is encountered in the road. My car literally will coast for 5-10 seconds WITHOUT any brake force at all if a bump in the road sets off the ABS during hard braking.
I don't think what you are describing is even mechanically possible...
Dan <----glad to be out of the car business

Outnumbered
03-25-2007, 10:12 PM
I don't think what you are describing is even mechanically possible...
Dan <----glad to be out of the car business
Typical service writer response..."could not duplicate problem". Like the customer has nothing better to do then waste time at the dealer service department making shit up:rolleyes:
I think he is maybe a little long on his time frame of 5-10 sec because it seems like forever when you are not slowing down but I can tell you this exact same thing happened to me but it always was on a hill with rough terrain. It was one of the reasons I converted to Dodge. The others being the fuel injector and fuel pump issues in the same 1998 2500 4x4. All replaced under warranty. That truck was a POS.

dicudmore
03-25-2007, 10:21 PM
Typical service writer response..."could not duplicate problem". Like the customer has nothing better to do then waste time at the dealer service department making shit up:rolleyes:
I think he is maybe a little long on his time frame of 5-10 sec because it seems like forever when you are not slowing down but I can tell you this exact same thing happened to me but it always was on a hill with rough terrain. It was one of the reasons I converted to Dodge. The others being the fuel injector and fuel pump issues in the same 1998 2500 4x4. All replaced under warranty. That truck was a POS.
not at all John, and I totally believe your several foot description, having driven EVERY GM/Chrysler product made from mid 90's (MOPAR) to current (GM)...have felt what you described MANY times, but not what he said...
also, "could not duplicate" is different than "not physically fockin' possible" :wink:

Outnumbered
03-25-2007, 11:16 PM
not at all John, and I totally believe your several foot description, having driven EVERY GM/Chrysler product made from mid 90's (MOPAR) to current (GM)...have felt what you described MANY times, but not what he said...
also, "could not duplicate" is different than "not physically fockin' possible" :wink:
Sorry if I sounded a little harsh. That truck just caused me so much grief and I don't know how many times I took it in and they told me it was fine. So when I read these posts on here telling Oliver that his ABS is normal it just brings back bad memories of frustration:mad::)

dicudmore
03-26-2007, 09:56 PM
Sorry if I sounded a little harsh. That truck just caused me so much grief and I don't know how many times I took it in and they told me it was fine. So when I read these posts on here telling Oliver that his ABS is normal it just brings back bad memories of frustration:mad::)
haha I can now relate to all of it again and relive the past myself...just traded my 05 Dually/Duramax for a 99 'Burb--ah the good ole days of shiat that dont stop :)

Outnumbered
03-26-2007, 11:03 PM
haha I can now relate to all of it again and relive the past myself...just traded my 05 Dually/Duramax for a 99 'Burb--ah the good ole days of shiat that dont stop :)
Just get one of these and call it good...
http://www.2see1.com/images/101_0198.JPG