ABS light wont go off

[Timon07]

I have a 1994 Pontiac Grand Prix with about 85,000 miles on it. It is in very good condition and is kept up. I have recently noticed that my abs light is on, and will not go off. It has been on for several months. I just got the back brakes change and the light still stayed on. A friend tried to get the codes off of the car and the codes would not come off for some reason. I am confsued and need some major help on this problem, my inspection sticker is going to expire soon... thanks

[Madmunky]

Originally Posted by Timon07

my inspection sticker is going to expire soon...

Oh how I love Canada, we only have to have our cars safetied when we buy them...
The only thing I could of suggested was what I had go wrong with my 95, but you already did the rear brakes, so I'm at a loss. There is another thread right now covering a very similar topic, maybe you can find some help in there? http://www.automotiveforums.com/vbul...d.php?t=528860
good luck

Jamie

[richtazz]

You'll have to have it scanned with an ABS capable scanner. The front ABS sensors are separate from the hubs, and pick up their signal from a reluctor on the CV axle. The rear wheel speed sensors are part of the rear hub bearing, and have to be replaced as a unit. Most do-it-yourself scan tools are not ABS capable (neither are the ones they use at Advance and Auto-Zone), so you may have to take it to a repair facility to find out which wheel has the offending sensor. It could also be a bad ABS module, pump or valve, but wheel speed sensors are the biggest offender.

[1typhoon]

First of all the brakes have absolutely nothing to do with your ABS light being on. It is fairly easy to check out an ABS system. 99 times out of 100 the problem is a wheel sensor. All you need is an ohm meter. Unplug the connector at each wheel sensor and measure the sensor resistance. it should be around 1K ohms or so. If it is open or shorted it is bad and needs to be replaced. If you can screw in a light bulb you can change it. Very easy.

[Madmunky]

Originally Posted by 1typhoon

First of all the brakes have absolutely nothing to do with your ABS light being on. It is fairly easy to check out an ABS system. 99 times out of 100 the problem is a wheel sensor. All you need is an ohm meter. Unplug the connector at each wheel sensor and measure the sensor resistance. it should be around 1K ohms or so. If it is open or shorted it is bad and needs to be replaced. If you can screw in a light bulb you can change it. Very easy.

If it has nothing to do with the brakes...then why is it an Antilock Brake System light?? Does ABS stand for something else that I'm not aware of?? and why did swapping my rotors and calipers make it go away? (no, I didn't touch the sensors)
Maybe they should just stop putting ABS lights on cars if they have nothing to do with brakes.
Jamie

[richtazz]

If your brake rotors are warped, causing a severe pulsation, or if one caliper is seized causing one wheel to drag, the ABS light will trip. ABS has everything to do with the brakes. The ABS module regulates brake line pressure, that is how ABS works. If the ABS module senses a wheel locking (because it's wheel speed sensor is registering a lower speed than the rest). it limits brake pressure to the locking wheel to prevent it from skidding. When the ABS module no longer gets a signal from a wheel speed sensor, it trips the light to let the driver know there is a problem, and may disable the ABS system completely. Until you get the car checked, drive more cautiously, as you may not have ABS when you need it.

[1typhoon]

Originally Posted by Madmunky

If it has nothing to do with the brakes...then why is it an Antilock Brake System light?? Does ABS stand for something else that I'm not aware of?? and why did swapping my rotors and calipers make it go away? (no, I didn't touch the sensors)
Maybe they should just stop putting ABS lights on cars if they have nothing to do with brakes.
Jamie

Dude, read the original post. He changed his brakes on the rear (meaning pads and or rotor). Rear pads and rotors or even calipers will not cause the ABS light to come on or off. The rear sensor is located in the rear hub assembly. The front sensor senses from the internal rotor or half shaft. His problem could be a rear sensor in the hub, or a front sensor in which case it could be the sensor or the rotor. As I stated before. The ABS system does not know or care the stae of yopur brake pads, rotors or calipers. I have worked on humdreds of these systems and 99 times out of 100 there is a bad sensor.

[1typhoon]

Originally Posted by richtazz

If your brake rotors are warped, causing a severe pulsation, or if one caliper is seized causing one wheel to drag, the ABS light will trip. ABS has everything to do with the brakes. The ABS module regulates brake line pressure, that is how ABS works. If the ABS module senses a wheel locking (because it's wheel speed sensor is registering a lower speed than the rest). it limits brake pressure to the locking wheel to prevent it from skidding. When the ABS module no longer gets a signal from a wheel speed sensor, it trips the light to let the driver know there is a problem, and may disable the ABS system completely. Until you get the car checked, drive more cautiously, as you may not have ABS when you need it.

A warped rotor will NOT cause an ABS code. Worn brake pads will NOT cause an ABS code. If a caliper is seized and the wheels still rotate at the same speed as the others, this will NOT cause an ABS code. If the wheel were LOCKED, then you would get a code, but then only if you could get the car to move, if that were the case the car would not be drivable.

[Madmunky]

Originally Posted by 1typhoon

Dude, read the original post. He changed his brakes on the rear (meaning pads and or rotor). Rear pads and rotors or even calipers will not cause the ABS light to come on or off. The rear sensor is located in the rear hub assembly. The front sensor senses from the internal rotor or half shaft. His problem could be a rear sensor in the hub, or a front sensor in which case it could be the sensor or the rotor. As I stated before. The ABS system does not know or care the stae of yopur brake pads, rotors or calipers. I have worked on humdreds of these systems and 99 times out of 100 there is a bad sensor.

So it hasn't got anything to do with his situation, but you saying that ABS light has nothing to do with brake is VERY misleading, like richtazz said "ABS has everything to do with the brakes." sure most of the time it is a sensor, but it can be the rotors or calipers, and don't dare say I'm wrong cause I swapped out my caliper and the light went away. I say it again, if ABS light has nothing to do with your brakes...why is it an Antilock Brake System light? coincidence? I think not!

Jamie

[1typhoon]

Originally Posted by Madmunky

So it hasn't got anything to do with his situation, but you saying that ABS light has nothing to do with brake is VERY misleading, like richtazz said "ABS has everything to do with the brakes." sure most of the time it is a sensor, but it can be the rotors or calipers, and don't dare say I'm wrong cause I swapped out my caliper and the light went away. I say it again, if ABS light has nothing to do with your brakes...why is it an Antilock Brake System light? coincidence? I think not!

Jamie

Sorry, but it CAN NOT be rotors or calipers.......your wrong.

[Madmunky]

Originally Posted by 1typhoon

A warped rotor will NOT cause an ABS code. Worn brake pads will NOT cause an ABS code. If a caliper is seized and the wheels still rotate at the same speed as the others, this will NOT cause an ABS code. If the wheel were LOCKED, then you would get a code, but then only if you could get the car to move, if that were the case the car would not be drivable.

then PLEASE...explain to me, why did swapping out my seized caliper make the light go away? is it a mirical of modern science?

Jamie

[richtazz]

But if he used an impact wrench while doing the brakes, he could have damaged the wheel speed sensor. A severe brake pulsation from warped rotors, or a dragging brake caliper can cause an abs light to trip, as can a low tire. The ABS computer senses that wheel rotating slower than the rest and will trip the light. I've worked on many GM minivans that have an issue with brake dust building up in the rear drums, causing the rears to get grabby. That will also cause an ABS light to come on, even though there is no real problem. So it is VERY possible bad rear brakes can cause an ABS light, whether the vehicle is rear disc or drum. The newer cars with low tire pressure warning lights work of wheel speed sensor readings, a low tire spins slower than the rest. Never say never.

[Madmunky]

Originally Posted by richtazz

But if he used an impact wrench while doing the brakes, he could have damaged the wheel speed sensor. A severe brake pulsation from warped rotors, or a dragging brake caliper can cause an abs light to trip, as can a low tire. The ABS computer senses that wheel rotating slower than the rest and will trip the light. I've worked on many GM minivans that have an issue with brake dust building up in the rear drums, causing the rears to get grabby. That will also cause an ABS light to come on, even though there is no real problem. So it is VERY possible bad rear brakes can cause an ABS light, whether the vehicle is rear disc or drum.

that means...seized caliper = slower wheel = ABS light...I understand why it works now....only if 1typhoon would

btw...I have a certified mechanic sitting right here saying the same thing Richtazz just said...and thats what I learned in grade 10 autoshop...

Jamie

[1typhoon]

I guess it could be a miracle or maybe sun spots, I guess it was just a coincident.
I still stand by my statements.
...or maybe an alien ship with a fusion drive operating near by.....

[1typhoon]

Originally Posted by Madmunky

that means...seized caliper = slower wheel = ABS light...I understand why it works now....only if 1typhoon would

btw...I have a certified mechanic sitting right here saying the same thing Richtazz just said...and thats what I learned in grade 10 autoshop...

Jamie

In my many years of travel I have found most "certified mechanics" barely made it to grade 10.