ABS almost fixed itself. Question?
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 905
Likes: 1
From: New Bern NC
ABS almost fixed itself. Question?
I have always had an ABS light on and no ABS. Today, I did a quick stop in the rain and THAT somehow caused the ABS light to go out. Good news so far. Now the light is out but the ABS is doing weird things. Driving at less thna 5mph and slowly apply the brakes will cause the ABS to THINK I am skidding and not let me stop. It does stop eventually but it kind of pulsates to a stop.
Any clues? Things to check? Tonight, I am taking out the rear speakers and reseating all the plugs on the ABS things back there.
Any clues? Things to check? Tonight, I am taking out the rear speakers and reseating all the plugs on the ABS things back there.
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 905
Likes: 1
From: New Bern NC
Re: ABS almost fixed itself. Question? (Tom Piper)
My guess is a wheel speed sensor.
Try to get the error codes.
Tom Piper
Try to get the error codes.
Tom Piper
Burning Brakes
Joined: Nov 2001
Posts: 1,241
Likes: 9
From: Houston TX
Re: ABS almost fixed itself. Question? (tworottiedogs)
are other people running C5 rims successfully? what tire sizes are you using, maybe there's too much difference in circumference between front and rear.
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Racer
Joined: Jul 2002
Posts: 412
Likes: 0
From: corvallis or
Re: ABS almost fixed itself. Question? (tworottiedogs)
The low speed pulsation is called "false modulation" or "unwarranted activation". This is caused when the computer thinks there is a wheel speed diferance that does not actually exist. The 2 most common causes are electrical resistance in the connection and metalic brake dust particles built up on the magnet of the speed sensor. 1st You can unplug each sensor clean with spray electronic cleaner and coat with dielectric grease then plug back in. 2nd you can use a nylon type brush (tooth brush) to remove any loose particles on the sensor magnet then spray off with the same elctronic cleaner. ABS is electronically controlled and operated via sensors and solonoids so almost always the problem is on the input side of the computer.
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
Re: ABS almost fixed itself. Question? (jefft84)
The car is in the garage right now, so excuse me for asking for clarification, but are you saying these sensors are easily accessible and just come off by "unplugging?" Could you please explain, I'm sure I'll be able to follow tommorrow when I'm out by the car.
"....so almost always the problem is on the input side of the computer", not sure what I'm looking for here!
Thanks for your help.
"....so almost always the problem is on the input side of the computer", not sure what I'm looking for here!
Thanks for your help.
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 905
Likes: 1
From: New Bern NC
Re: ABS almost fixed itself. Question? (jefft84)
???
I was going to pull them for cleaning. Do we just clean the outside? Sounds easy but why??
They dont have to come off to be cleaned
Racer
Joined: Jul 2002
Posts: 412
Likes: 0
From: corvallis or
Re: ABS almost fixed itself. Question? (tworottiedogs)
All the sensor consist of is a magnet encased in plastic with a wire on the + and - side to create a pulse signal as the "tone ring" the toothed wheel turns past it. The sensor itself has no moving parts, the magnet end can get debris stuck to it blocking the signal causing improper or no ABS activity. Cleaning this off usually restores proper signal and operation. Just clean it off on the car if you remove it you run the risk of breakage.
[Modified by jefft84, 10:10 AM 3/14/2003]
[Modified by jefft84, 10:10 AM 3/14/2003]
Drifting
Joined: May 1999
Posts: 1,478
Likes: 3
From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
Re: ABS almost fixed itself. Question? (tworottiedogs)
On the early model C4s the ABS does not set retrievable codes.
To clean the sensors look at the wheel knuckle and you will see a 10mm hex head screw. It will be clamping down the sensor inside the knuckle. The ABS connecting wire cable will be coming off the back of the sensor and going inot the chassis and eventually to the ABS controller behind the driver seat. With a wrench or socket unscrew the small clamp and pull the sensor out of the knuckle (do not pull using the sensor wire!).
As already mentioned, use electronic spary cleaner or WD-40 to aid in brushing off the end of the sensor. That end is open to the outside environment and the powerfull magnet attracts all kinds of metalic dust and bits of junk over time. Put some anti-sieze on the steel sides of the sensor where it contacts the aluminum wheel knuckle so it doesn't sieze up. (Similar to the spark plugs seizing in the aluminum heads of 86+ vettes)
It is REAL easy to do this with each wheel off the car, but wheel removal is not necessary. You can easily clean all 4 sensors without removing the wheels in about 20 minutes (~5 minutes each). It takes about 40 minutes the first time and under 20 once you have done it before. The only tool needed is the wrench or socket for the hold down screw.
To clean the sensors look at the wheel knuckle and you will see a 10mm hex head screw. It will be clamping down the sensor inside the knuckle. The ABS connecting wire cable will be coming off the back of the sensor and going inot the chassis and eventually to the ABS controller behind the driver seat. With a wrench or socket unscrew the small clamp and pull the sensor out of the knuckle (do not pull using the sensor wire!).
As already mentioned, use electronic spary cleaner or WD-40 to aid in brushing off the end of the sensor. That end is open to the outside environment and the powerfull magnet attracts all kinds of metalic dust and bits of junk over time. Put some anti-sieze on the steel sides of the sensor where it contacts the aluminum wheel knuckle so it doesn't sieze up. (Similar to the spark plugs seizing in the aluminum heads of 86+ vettes)
It is REAL easy to do this with each wheel off the car, but wheel removal is not necessary. You can easily clean all 4 sensors without removing the wheels in about 20 minutes (~5 minutes each). It takes about 40 minutes the first time and under 20 once you have done it before. The only tool needed is the wrench or socket for the hold down screw.
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 905
Likes: 1
From: New Bern NC
Re: ABS almost fixed itself. Question? (Mike_88Z51)
On the early model C4s the ABS does not set retrievable codes.
To clean the sensors look at the wheel knuckle and you will see a 10mm hex head screw. It will be clamping down the sensor inside the knuckle. The ABS connecting wire cable will be coming off the back of the sensor and going inot the chassis and eventually to the ABS controller behind the driver seat. With a wrench or socket unscrew the small clamp and pull the sensor out of the knuckle (do not pull using the sensor wire!).
As already mentioned, use electronic spary cleaner or WD-40 to aid in brushing off the end of the sensor. That end is open to the outside environment and the powerfull magnet attracts all kinds of metalic dust and bits of junk over time. Put some anti-sieze on the steel sides of the sensor where it contacts the aluminum wheel knuckle so it doesn't sieze up. (Similar to the spark plugs seizing in the aluminum heads of 86+ vettes)
It is REAL easy to do this with each wheel off the car, but wheel removal is not necessary. You can easily clean all 4 sensors without removing the wheels in about 20 minutes (~5 minutes each). It takes about 40 minutes the first time and under 20 once you have done it before. The only tool needed is the wrench or socket for the hold down screw.
To clean the sensors look at the wheel knuckle and you will see a 10mm hex head screw. It will be clamping down the sensor inside the knuckle. The ABS connecting wire cable will be coming off the back of the sensor and going inot the chassis and eventually to the ABS controller behind the driver seat. With a wrench or socket unscrew the small clamp and pull the sensor out of the knuckle (do not pull using the sensor wire!).
As already mentioned, use electronic spary cleaner or WD-40 to aid in brushing off the end of the sensor. That end is open to the outside environment and the powerfull magnet attracts all kinds of metalic dust and bits of junk over time. Put some anti-sieze on the steel sides of the sensor where it contacts the aluminum wheel knuckle so it doesn't sieze up. (Similar to the spark plugs seizing in the aluminum heads of 86+ vettes)
It is REAL easy to do this with each wheel off the car, but wheel removal is not necessary. You can easily clean all 4 sensors without removing the wheels in about 20 minutes (~5 minutes each). It takes about 40 minutes the first time and under 20 once you have done it before. The only tool needed is the wrench or socket for the hold down screw.
I did the rear abs sensors today. I had the car apart to replace the halfshaft u-joints so I figured doing the ABS sensor would be a good thing. Crazy thing is, IT WORKED!!! I did only the rear and the light is GONE!!
Here are a couple of pics for anyone that want to do this.
:D :D :party: [Modified by tworottiedogs, 8:02 PM 3/15/2003]
Racer
Joined: Jul 2002
Posts: 412
Likes: 0
From: corvallis or
Re: ABS almost fixed itself. Question? (tworottiedogs)
GREAT PIC!! showing the metal crud sticking to the sensor :thumbs:
Its amazing how many sensors get replaced that just need to be cleaned and good connection restored.
Its amazing how many sensors get replaced that just need to be cleaned and good connection restored.
