Bad ABS Sensor

[99GTCoupe]

Or at least I think so. The guy I had bought the car from said that the ABS sensor was needing to be replaced. After some driving or after harsh bumps in the road (damn Michigan patchwork) the tone will sound and the ABS and Trac Off light will come on. Now, I have been wanting to get an actual Service Manual but I cannot afford to pay out for one yet.

I want to know a couple things:
1) Is this a relatively easy thing to replace? (I know I need to find out which sensor it is first, though)
2) Can anyone point me to a How-To Guide for this? or can it be described easily in a post or two without needing pics?

I tried searching here and Google, but couldn't find anything that seemed like what I am looking for. Thanks in advance.

[nascarnate326]

I would try your front hub. I think the left is more common to go out then right.
Not too hard, and i have no how to guide, sry.

[99GTCoupe]

Thanks, hopefully someone else will

I don't know if this helps but upon checking out my brakes as I walked past the car the other day, I noticed that I have 4-wheel disc brakes ^.^

1) Would that affect anything, assuming of course the conversion was done correctly?
2) Does that make changing the rear disc pads and rotors the same as doing the front? I would assume so, just want to make sure.

I will need to replace my brakes probably in about a month or so, not sure cause I don't hear the 'indicator' scraping noise, but they make a scraping/low-pitched-squeal noise sometimes when stopping. Stopping power is still good, so I know I have time before replacing them. If the front and back are relatively the same (yeah, I've replaced brakes before btw), then I will be doing the pads and rotors all around, just so I know things are all set

Any tips on either this post or the origianl post are greatly appreciated

[eaglesrealm]

First things first, the GT's come with 4 wheel disc's, so that should be a factory setup and nothing you need to worry about.

As for the brake work, if it were my car, I would take the time to investigate each seperately. I typically only change the rotor(s) that need changing, not just for the heck of it. At the same time, I would check the break pad thickness to gauge how much time you have left before the next change. Of course, pads are cheap, so if you really want new brakes....have fun! And yes, these are a piece of cake to change. The rotors can be fun, in that you have to take off the caliper bracket, and depending on how much lock-tite was used, you may break knuckle. First time I did the job, I wished I had an air wrench. Now, on successive jobs, they come out just fine with a breaker bar (since I do not change the bolts each time and re-lock-tite)

Finally, do you hear any noise at all from any of your wheel wells? Usually it will start as a low level hum that you only hear at slow speeds and will get worse over time. Our speed sensors are not usually the culprit in terms of failure, it's the actual wheel hub bearing assy itself. These have integrated speed sensors though, so you end up having to buy an entire wheel hub assembly. Only way to check is with a reader that can read ABS codes (which AutoZone, etc cannot)
I would suggest waiting until the code is on, but it might be storing them as softcodes and still be readable even once they are not on. Changing it is not that bad. I have posted this somewhere before.

The basic steps are (It's been a little while, but I think I can remember it all):

1) Break axle nut loose (Autozone, Murray's, etc will lend them to you)
2) Break lugnuts loose
3) Raise Car
4) Take off wheel
5) Remove caliper and hang it carefully by string, etc so you do not have to worry at all about it falling.
6) Remove rotor
7) Remove axle nut
8) Remove three bolts (come in from behind the hub) that hold the hub assy on.
9) Unplug the speed sensor
10) Slide off the hub assy (can be easier said than done, there is a hub puller to make it a little easier. I was able to tap mine off lightly with a lot of patience, but be careful not to detroy or seperate anything on the axle)
11) Reverse steps

Of course, this info is all informational only. Use at your own risk!!

[99GTCoupe]

Ah, thanks cause everything that I read said GA's came with 2-wheel disc (same for all models) but still nice to have
No hums, I've heard that before in a car but not on mine. I should have added above that no abnormal sounds (other than a rattling noise when I go over like train tracks and such coming from the rear, but that's another issue; I'm assuming struts >< ) from the brakes.

Also, I assume that the axle nut is behind the center cap on the wheels? And, uh, at the end you say to remove the hub assembly, then reverse the steps..... Where and how do you replace the ABS Sensor (I assume that's what these steps are for)?

[eaglesrealm]

Originally Posted by 99GTCoupe

Ah, thanks cause everything that I read said GA's came with 2-wheel disc (same for all models) but still nice to have
No hums, I've heard that before in a car but not on mine. I should have added above that no abnormal sounds (other than a rattling noise when I go over like train tracks and such coming from the rear, but that's another issue; I'm assuming struts >< ) from the brakes.

Also, I assume that the axle nut is behind the center cap on the wheels? And, uh, at the end you say to remove the hub assembly, then reverse the steps..... Where and how do you replace the ABS Sensor (I assume that's what these steps are for)?

I thought I had said somewhere in there that it was an integrated unit. If you buy the wheel hub assembly, it will have a speed sensor already built into it with a pigtail with a connector sticking out. Other than disconnecting and reconnecting that connection, there is nothing else to do related to the speed sensor. Maybe that was the problem, I keep calling it the speed sensor (which it is) - that is one in the same to the ABS sensor. The ABS unit uses wheel speed sensors to monitor and control the situation when needed.

On your other note, yes, just pop out the Plastic Pontiac emblem and you will see the axle nut. I believe that the axle nut socket was too big to fit through that opening, so I ended up just throwing the spare tire on, lowering the car back down, and then breaking the nut free. Extra steps, but much faster than trying to find a socket that would fit through there at another store.

[eaglesrealm]

"All Grand Ams come with anti-lock brakes, and the GT comes with four-wheel discs, too. Stopping ability and pedal feel are virtually world-class for a car of this price. Multiple hard stops produced only slight fade, about as much as many moderately priced German sedans we've tested."

Source:
http://www.thecarconnection.com/Vehi...S180.A948.html

[99GTCoupe]

Originally Posted by eaglesrealm

"All Grand Ams come with anti-lock brakes, and the GT comes with four-wheel discs, too. Stopping ability and pedal feel are virtually world-class for a car of this price. Multiple hard stops produced only slight fade, about as much as many moderately priced German sedans we've tested."

Source:
http://www.thecarconnection.com/Vehi...S180.A948.html

Thanks, honestly the sites I had checked out all said only 2-wheel disc,

Anyways, so in other words (abridged version), eaglesrealm, you take off the tire and hub assembly, making sure to unplug the speed sensor first, and then put on the new assembly?

I just want to make sure I am clear on everything:
the ABS Sensor is the exact same things as the Speed Sensor (one in the same), so in other words the Spped Sensor contains the ABS Sensor and the ABS Sensor feeds off info given by the Speed Sensor? Is that basically correct?
So I would need to go out and purchase a new hub assembly or a new speed sensor? or is the speed sensor integrated into the hub assembly? And so, in the end, it is more of a matter of replacing the hub assembly, not just a sensor, correct?
I ask because I thought I saw a ABS Sensor sold at AutoZone for the 99 GA GT.

[Roush GT]

^ correct you would need a new hub assembly

[eaglesrealm]

Originally Posted by SilverGT1

^ correct you would need a new hub assembly

Exactly. I happen to use Timken brand, which are usually around $130-$140 at Autozone. If you want, go to autozone.com and use the online shopping for your 1999 GAGT. When in the online "shopping" section, type in "Wheel" for a search keyword.

You should see the following come up from the search: (2 of the items at least)

Bearing/Hub Assembly - Wheel Front
Bearing/Hub Assembly - Wheel Rear

Click on the one you need, once you know.

And yes, the Wheel Speed Sensor and the ABS Sensor are two names for the same thing. And yes, it is integrated into the Bearing/Hub assembly, so there is no need to purchase a seperate sensor. I don't even think you can service them to replace just the sensor, as they are sealed units.

[99GTCoupe]

ARGH! Damnit GM! ><

[eaglesrealm]

Originally Posted by 99GTCoupe

ARGH! Damnit GM! ><

I used to say the same thing about this one, but it's actually not a bad idea.
It's a nice assembly, the one drawback is the actual bearing failure.

In the opposite case, where just the sensor fails, you will pay a lot more than you should have to. However, from what I have seen and heard, the bearing fails far more often than the sensor.

Would you save some money if you could replace just the bearing? Sure, but the sensor itself is not that expensive, it simply reads the tone markings inside the hub assy, which the ABS can turn into speed.

[tenspeed]

Before you buy a new hub, clean and lube the connections. A bad connection will give the same open coil signal as a bad sensor.

Put the front wheels up on ramps and look at the bottom for the gray two wire plug. Pull them apart and slide them back together a couple of times.

[99GTCoupe]

k, but clean and lube what with what?

, that just sounds diiiirty!

[AznGA]

Is this gonna be a huge problem if I just deal with it?

I have SVS, ABS, and Trac Off lights coming on once in a while. It only happens when I start my car and pull out of the parking spots. They dissappear when I start the car next time, and so on.

[eaglesrealm]

Originally Posted by AznGA

Is this gonna be a huge problem if I just deal with it?

I have SVS, ABS, and Trac Off lights coming on once in a while. It only happens when I start my car and pull out of the parking spots. They dissappear when I start the car next time, and so on.

The way I always answer this question is : It's not a huge problem, unless you are like me and never want to go without ABS. I not only work in the manufacturing of ABS and have seen the data associated with it's benefits, but I have used it many times, sometimes saving my from losing control of the vehicle with quick and last second adjustments for variety of reasons (car that stopped suddenly, deer, etc)

Don't let anyone fool you, the best driver in the world cannot simulate the control of ABS.

[99GTCoupe]

Right, well I will have to check things out when I replace my regulator and jack the car up to check the CV boot and struts

[tomh]

Originally Posted by tenspeed

Before you buy a new hub, clean and lube the connections. A bad connection will give the same open coil signal as a bad sensor.

Put the front wheels up on ramps and look at the bottom for the gray two wire plug. Pull them apart and slide them back together a couple of times.

lube with what?? i tried cleaning mine.. it wasnt that bad

[tenspeed]

Originally Posted by tomh

lube with what?? i tried cleaning mine.. it wasnt that bad

Di-electric grease. It's non-conductive silicone that seals and waterproofs electrical connections such as battery terminals and light bulbs. It prevents moisture and air from getting in and causing corrosion.

It's sort of a long shot that the connection is the problem but it's fast and easy to do.

[99GTCoupe]

Ah, so it would probably be a good idea to pick it up anyways, that way when I replace the hub assembly (if I have to), I'll just put that stuff on to prevent future issues