ABS unit activating prematurely

99-GMCSierraZ71 · 10-20-2009, 06:27 PM

Hi All,

I have a 99 GMC Sierra Z71 4X4, 5.3L, Auto, Short box

My ABS unit is activating prematurely, meaning when I depress the brake
pedal, frequently, the ABS unit thinks I am really "laying" on the brakes and the unit
activates, I took it in to get it scanned, nothing came up
on the computer for codes, the mechanic determined that the wheel sensors probably need cleaning (and\or) replacing

My question is...

Is this an expensive job? He told me that some trucks have the sensors
built into the hub and if it can't be cleaned, the hub has to be replaced,
he wasn't sure whether my truck was this type

Has anyone experienced this before? its going in next Tuesday to get fixed

PS, I already had replaced the whole ABS unit once on this truck in 2003,
about 40K ago (very expensive)

Thanks in advance for your help (comments)

Brian

mudseeker · 10-20-2009, 06:37 PM

common problem with the sensors at low speed.

leolkfrm · 10-20-2009, 07:07 PM

Have you ever flushed the system with new fluid? it may be getting thick and giving a false reading to the abs

99-GMCSierraZ71 · 10-20-2009, 08:34 PM

I am thinking the sensors are the problem too but we'll see, I am sure they will look at changing the fluid also

If it is the sensors and they do need replacing, is the make and model of my truck the type that need the whole hub replacing just to fix the sensor problem?

99 GMC Sierra 1500 Z71 4X4 shortbox

mudseeker · 10-20-2009, 08:53 PM

4x4 are usually a sealed hub, but not sure on that year.

BernieB · 10-21-2009, 02:04 AM

Very common problem with those sensors, and the subject of a limited recall here in the States. Not sure if it was a recall issue in Canada though.

99-GMCSierraZ71 · 10-21-2009, 10:44 AM

I just hope it doesn't cost me my first born to fix it LOL

Thanks for all your response

Brian

99-GMCSierraZ71 · 11-02-2009, 02:53 PM

**UPDATE**

Just got the truck worked on, it was the sensors, the mechanic took the hubs off and cleaned the sensors, they were pretty dirty and had some rust on them

He told me that the sensors are sealed in the hub and most shops would have just told me to replace the hubs to get more money out of me

In any case, he managed to get at them OK without replacing them, the truck stops fine now without the ABS kicking in, only cost me 150 bucks which is a relief

Thanks for all your help folks!

Brian

10-20-2009, 06:27 PM	#1
99-GMCSierraZ71 Junior Member Join Date: Oct 2009 Location: Nanaimo BC Canada Posts: 8	ABS unit activating prematurely Hi All, I have a 99 GMC Sierra Z71 4X4, 5.3L, Auto, Short box My ABS unit is activating prematurely, meaning when I depress the brake pedal, frequently, the ABS unit thinks I am really "laying" on the brakes and the unit activates, I took it in to get it scanned, nothing came up on the computer for codes, the mechanic determined that the wheel sensors probably need cleaning (and\or) replacing My question is... Is this an expensive job? He told me that some trucks have the sensors built into the hub and if it can't be cleaned, the hub has to be replaced, he wasn't sure whether my truck was this type Has anyone experienced this before? its going in next Tuesday to get fixed PS, I already had replaced the whole ABS unit once on this truck in 2003, about 40K ago (very expensive) Thanks in advance for your help (comments) Brian

10-20-2009, 06:37 PM	#2
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,373	common problem with the sensors at low speed. __________________ i'd rather be hunting

10-20-2009, 07:07 PM	#3
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 4,300	Have you ever flushed the system with new fluid? it may be getting thick and giving a false reading to the abs __________________ 4 wheels move the body 2 wheels move the soul B.W.A.I

10-20-2009, 08:53 PM	#5
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,373	4x4 are usually a sealed hub, but not sure on that year. __________________ i'd rather be hunting

10-21-2009, 02:04 AM	#6
BernieB Senior Member Join Date: Jul 2009 Location: Fredericksburg, VA Posts: 1,901	Very common problem with those sensors, and the subject of a limited recall here in the States. Not sure if it was a recall issue in Canada though. __________________ If the guys who design 'em had to take one home, use it every day for 2 years, and do all the maint and repairs themselves, cars would have a button on the dash to change the oil, filters & plugs.

10-20-2009, 08:34 PM	#4
99-GMCSierraZ71 Junior Member Join Date: Oct 2009 Location: Nanaimo BC Canada Posts: 8	I am thinking the sensors are the problem too but we'll see, I am sure they will look at changing the fluid also If it is the sensors and they do need replacing, is the make and model of my truck the type that need the whole hub replacing just to fix the sensor problem? 99 GMC Sierra 1500 Z71 4X4 shortbox

10-21-2009, 10:44 AM	#7
99-GMCSierraZ71 Junior Member Join Date: Oct 2009 Location: Nanaimo BC Canada Posts: 8	I just hope it doesn't cost me my first born to fix it LOL Thanks for all your response Brian

11-02-2009, 02:53 PM	#8
99-GMCSierraZ71 Junior Member Join Date: Oct 2009 Location: Nanaimo BC Canada Posts: 8	UPDATE Just got the truck worked on, it was the sensors, the mechanic took the hubs off and cleaned the sensors, they were pretty dirty and had some rust on them He told me that the sensors are sealed in the hub and most shops would have just told me to replace the hubs to get more money out of me In any case, he managed to get at them OK without replacing them, the truck stops fine now without the ABS kicking in, only cost me 150 bucks which is a relief Thanks for all your help folks! Brian

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