Thread: ABS Issue

Wow, I was away for a while because I was busy and unable to get to a computer and there's quite a bit of posts in this thread. BTW thank you for that image, it helps a LOT! I was looking on ebay and the pictures were showing a silver control-module so it made me think it was separate. They were probably using a default image of something else. I'll probably just go to junk yard, and pull the whole module my self.

Thanks for the picture dstout, I'm pretty sure mine looks quite similar. My dad and I are going to pick up a replacement at a junk yard hopefully.

As for you being able to replace the control module apart from the actual abs module, yes, you can. The mechanic that checked it said there are several parts you can service yourself, the control module being one of them. He said that, if you really wanted to, you could replace the little motors inside of the abs module that control which brake gets how much power etc . . . I just need to get the parts and replace it. A junk yard will probably sell the control module with the abs module, most places don't find it worth-it to remove them from each other. Most people usually replace the whole unit anyways.

I work in a drivline shop and have seen a bad wheel bearing that will set off the abs and trac. light. It has done it on my 04 GTP and never had a problem since I changed the bearing. The issue is that there is play in the bearing and it will hit the sensor and give it a bad signal. When you turn the car off, it will reset and the lights will go out. Like I said, it always did it in my 04 and after replacement there have been no issues. Not guarantee, but something else to look into.

UPDATE: I started shopping for the ABS control unit, Morad has one for $50. I signed up at a parts finder website and have gotten emails ranging from $75-$150. Called a few places local here and nobody has one.

From what I've heard, it's fairly common to replace just the electronic module.

As it turns out, I took it in for another scan before ordering the part, and it throwing a code for LF wheel sensor. I just replaced that one last year, so the garage is going to warranty the part. The hub/sensoor assy is over $200 just for the part.

Originally Posted by dstout

I'm glad the picture helped you out
If you do find a good module in the junk yard and you have to remove it yourself....just cut the brake lines above the fittings about an inch, don't unscrew the fittings from the module untill you are ready to install it. If you keep it upright it wont leak or you can crimp the ends of the stubs shut.

I'm guessing this will make it so that I don't have to worry about air bubbles in the abs and will make it easier to bleed the brakes once I'm done?

Originally Posted by nfloyd2006

I work in a drivline shop and have seen a bad wheel bearing that will set off the abs and trac. light. It has done it on my 04 GTP and never had a problem since I changed the bearing. The issue is that there is play in the bearing and it will hit the sensor and give it a bad signal. When you turn the car off, it will reset and the lights will go out. Like I said, it always did it in my 04 and after replacement there have been no issues. Not guarantee, but something else to look into.

My dad and I really like to use GM's 3.8 and we've had 3 of them now that have abs. We've seen the same thing. Its just there was only 1 wheel sensor that was throwing a code and it was the LF. That one and the RF are pretty new, not to mention there was only one instance of that code in the memory and when my dad and I had that wheel off before getting it checked we saw that the connection wasn't hooked up to the bracket so it was swaying, when we disconnected the wires we saw a lot of corrosion, we cleaned it up and put some dielectric grease on it and it didn't throw another code. The mechanic took it down a dirt road (actually the dirt road he and I both live on) and drove it up and down it. The road has some nice sharp curves and he made some "ABS stops" making sure to stop on really loose gravel to make the abs go off. He got both lights to trip, but all of the wheel sensors showed they were fine, and none of them tripped, so he said he strongly thinks its not a wheel sensor, but I have seen that happen before.

so I am assuming that this turned out to be the LF wheel and all has been well since this last post?

No, I was getting more than one code, the LF wheel was just one of them. My dad and I took off all 4 wheels to see the condition of the wires and the bearings and there weren't any issues with any of them except the LF sensor wire wasn't attached to its bracket, we disconnected it, cleaned up the leads because they were corroded and then put some di-electric grease on the connections then re-connected it. I took it in a wheel later, when the mechanic hooked it up to the sensor he said it showed that about a week ago it threw a LF sensor but that he didn't see one since, and that he saw quite a few other codes thrown, so he cleared the codes, took it for a drive, swerved a few times to see how good of condition the bearings were in (also sometimes if its a bearing going out, then moving the steering wheel back and forth can cause the sensor to throw, and he said he couldn't get any of the wheel sensors to throw, then he took it down a dirt road, then he pushed on the breaks hard a couple times on loose gravel and all 4 sensors showed they worked just fine. He got it to act up again, however, and it showed nothing to do with that wheel, in fact, it was throwing what he called a false code. It said a couple of times that the RR sensor was throwing when it wasn't, and there were quite a few other codes thrown. When he looked them up on the system it said "usually these codes are thrown when one or multiple motors in the ABS module are going out".

Your ABS module connects between the master cylinder and the breaks. It puts more or less pressure on individual wheels depending on if their gripping or sliding. It does this by little motors, one for each wheel. when you stop and one wheel isn't getting traction, it puts less pressure to that wheel but turning that motor a little less, and by putting a little more pressure on the other wheels so the car can stop straight (if a wheel locks up then thats when you start to slide). Its one of two of those motors going bad.

Another 1 or 2 codes that are being thrown deal with the control module itself. he said that they can go bad sometimes, especially on a car with over 100,000 miles. He said it would be a good idea to replace both because there could be an issue with both. He said it may just be the control module not allowing the motors to work properly but he said he doubted it. So no, we haven't fixed the issue yet.

rofl the abs was like HOLY CRAP ! How the heck are you making this tire go so fast?

I have a 2003 GTP and I am having a similar problem with intermittent ABS traction control light coming on, also intermittently I can feel the ABS motor running (through the brake pedal) when I make light to average stops like I am trying to stop as if it was slick out and the ABS light or traction control light will not be illuminated. Ordered a scanner to trouble shoot I will post my findings.

Since this is the newest thread concerning ABS questions, I would like to throw in what is going on with mine. Maybe someone has seen this? I picked up a 1994 SE with 4 wheel disc brakes for nothing 2 weeks ago. The ABS and the BRAKE lights have been on since I got it. As I drove, I could hear the rears dragging, figured the calipers were hanging up. Took the rear wheels off and found alot of corrosion. The rotors were rusted and grooved, the parking brake levers were seized up, ect. So I replaced calipers, pads, rotors, hardware and so on. Go to bleed the brakes, and the Chiltons manual says you cannot manually bleed the brakes until the ABS is repaired and the codes cleared. I decide to try it anyway, I need to drive the car! I bleed the rears, all seems good and the next morning, drive to work and the brakes feel alright. On the way home, the pedal feels spongy... Hmmm must still be air in there. Get home, have my "assistant" operate the pedal and I will operate the bleeders. To my surprise, as the pedal is being pumped, I notice the calipers are not compressing the pads onto the rotor. They work with the parking brake however. I open the bleeder and NO fluid. Not even air. And, when I open the bleeder, my assistant is telling me the pedal does not move!?!?! This is when I realized the car has been using only front brakes since before I got it!!!So, to check and see if fluid is even flowing to the back, I loosen the lines to the rear at the ABS pump... MY assistant is STANDING on the brake pedal and NO fluid is coming out!!! I am, however, able to bleed the hydraulic modulator/master cylinder and the front brakes. Could the solenoid for the rears be stuck? I removed them both and could not see any difference (open/closed). I thought if I switched the solenoids and the problem switched from the rear to the front, then that would be my answer? Tomorrow, I am going to find a local shop with the scan tool needed to retrieve the codes. I have a pretty good one, but it is not able to read ABS diagnostics. Of coarse! Any input would be greatly appreciated! Thanks!

Wow, interesting problem. at first when you were just talking about the ABS light and the Break light being on I first though of the parking break. Not many people know this, but the parking break doesn't normally use any fluid, it just has a line that goes to the back breaks, and it ensures that the back breaks stay compressed. (not sure if this is that way in all cars or not). There is a sensor that when the parking break is pushed, turns on the break light and turns off the abs (hence turning on the ABS light).

A lot of times when I've seen this issue, someone will park a car they haven't used in a while, and they put on the parking break. You commonly will find that the parking break cable has corrosion on it, preventing it from working, and you can find many rear-break issues, which it sounds like you have. If both of those lights are still on, I would look into getting the parking break working. Make sure that it moves smoothly and then if the lights still come on, see if its the sensor (a mechanic could also code the car to see what codes are being shot out, and that should tell you if your car thinks your parking break is engaged.

Now, someone told me that when the parking break is engaged, it disengages the pump for the rear breaks. Not sure if that's true or not, but it could explain why you can't bleed them, and this all could explain why they were dragging to begin with.

Anyways, I would start by looking at the parking break!

Thanks for your reply! The parking brake is working perfectly, and worked perfectly before I started any work on the back brakes. In fact the parking brake is the only way I can get the calipers to compress/operate! I will check the parking brake light switch at the pedal to see if it is stuck closed or if there are any shorts in the parking brake warning lamp circuit. If what that someone told you is true about the rear ABS pump being disengaged when the parking brake is on, that could very well be my problem! A simple short in the warning lamp circuit!!!
I did stop by a local shop yesterday and asked if they could retrieve the codes. I told him upfront that it was a 94 and he said "yup! $20" when he walked out to the car he was holding a scanner with a OBDII plug. I reminded him the car is a 94 and the data plug is ALDL. He came back a minute later with a much larger scan tool, sat in the car and began programming it. Just then the owner came over and asked what the car was doing. I explained what the car is doing and he said, " let me save you some time and aggravation. Go to a junk yard and get the entire control unit/master cylinder/pump assembly, replace it and you will be fixed." Without even reading the codes!!! Just because it is not a simple OBDII plugin, no one wants to be bothered!!! At least I did not have to pay him...
What I was also thinking about, The master cylinder/pump assembly is also the proportioning valve. On my car without ABS, if the proprtioning valve is not operating properly (no pressure to the rear brakes) the parking brake warning lamp will light. So, in this case, if the pump that operates the rear is no good, the system would would sense a lack of pressure to the rear and light both lamps...
Well, I am going to check the parking brake switch. Thankyou for your suggestion. Ill keep you posted.

I'll make an addition in case someone wants to throw their .02 my way.

Since i bought the car with 90,000 miles in '07 the tcs light has been on. About a year later the abs light came on out of nowhere. Spraying electrical cleaner on the connections to the hubs would make the light go off for a little while, but would be right back on after turning it off and back on.

Another thing that seems strange to me is that sometimes the abs light will blink. When it does this, it blinks faster and faster as I increase speed until ultimately it either stays on, or goes off. When I slow back down or come to a stop it comes back on, without fail.

I havent gotten it scanned partially because I thought the only place that had a scanner for it was a dealer and they want $90 just to scan, so thats what discouraged me from doing that. If anyone knows a cheaper place around rochester, michigan ide appreciate it.

Another question on replacing the abs module, I understand its 2 pieces. The electronic piece can be replaced fairly easily by unscrewing it and not having to disconnect the brake lines? And to replace the "motor" part of it requires disconnecting the brake lines? Thanks guys for the help!

Oh, I've never seen a low tire pressure light either.

I think you'll find that there's either a short in one of the wires leading to a sensor or one of your wheel sensors are going out, that's a tough one though. I got mine scanned at a discount tire for $39. My car is OBD-II.

First, it depends on the year of your car. I'll use a quote from OBD-II - On-Board Diagnostic System to explain why:

All cars and light trucks built and sold in the United States after January 1, 1996 were required to be OBD II equipped. In general, this means all 1996 model year cars and light trucks are compliant, even if built in late 1995.

IF your car has OBD-I then you should be able to take it into an autozone and have it scanned free (so I've been told), and if its OBD-II then they can't. I would start by calling a local autozone first, ask them if they have a scan tool that can scan your year of grand prix for abs issues, they will be able to tell you whether they can or not and if you ask them they should be able to tell you if its OBD I or II. IF it has obd-II then call up local tire shops, maybe "Rochester hills tire & services" or Discount tire, or Belle tire. Any of them SHOULD have a scanner (make sure to call and ask though).

thanks for the reply. ill call up discount today and see what they say. its a 2000 so its got obd2, so it needs to tech 2 scanner or whatever to scan body codes.

ive replaced the front passenger side because it went bad, but had no effect on the abs light. Also, got a front driver's side a few weeks ago just to see if plugging it in would help, didnt work. Does it need to be bolted to the car for the sensor to work? Whatever I do with the rears, play with the wires or spray the connectors with cleaner, it doesnt do anything so I'm leaning towards something in the front going bad or the module itself... will find out soon, its been about a year and a half and I dont want to go through another winter without it.

I got my abs module from a junk yard, and I need to know what I should do to properly bleed it. We just hooked it up and my dad has the idea to have me push on the brake pedal, he'll loosen up a line, let it push the air out then while i hold the break he'll hook it back up and do that for all 4. And then work on the bleeders. Is there any way better than this to bleed the ABS module?

ALSO . . .
Do I have to/Should I bleed the 4 wheels also? Or is that not necessary if we bleed the abs unit well enough?