Most common ABS problems.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
Rumors
have heard that law enforcement agencies routinely disable the ABS due to complaints by operators (LEO's) that braking is compromised by the ABS rather than aided.
have heard that the LAS (lateral accel sensor), that MUST disable the ABS during turns to prevent ABS braking reduction at one side from causing loss of control, will also shut off the ABS if the vehicle is in a skid sideways (just when most needed)
have heard that some owners unplug the electrical connector in the ABS compartment and remove the ABS warning bulb from the DIC and enjoy better brake performance and 'pedal feel'.
have heard that a local owner of a GM pick-up truck that was only weeks old, rammed the side of the local convenience store when a small piece of rust somehow found its way into the ABS sensor interface, causing the ABS to activate and reduce brake function at one wheel (how all ABS operates AFAIK) , extending stopping distance to beyond the building exterior surface.
i RECOMMEND that you do no modifications to your brake system in any manner.
have heard that the LAS (lateral accel sensor), that MUST disable the ABS during turns to prevent ABS braking reduction at one side from causing loss of control, will also shut off the ABS if the vehicle is in a skid sideways (just when most needed)
have heard that some owners unplug the electrical connector in the ABS compartment and remove the ABS warning bulb from the DIC and enjoy better brake performance and 'pedal feel'.
have heard that a local owner of a GM pick-up truck that was only weeks old, rammed the side of the local convenience store when a small piece of rust somehow found its way into the ABS sensor interface, causing the ABS to activate and reduce brake function at one wheel (how all ABS operates AFAIK) , extending stopping distance to beyond the building exterior surface.
i RECOMMEND that you do no modifications to your brake system in any manner.
Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
Find a shop that will let you watch what they do or buy your own Tech 1 for about 1800 if you can find one. I have never heard my ABS self test the light blinks and that is it and it has never gone off no matter how hard I try. If the ABS needs bleeding it is going to be messy and hard to avoid send a letter to GM about the poor design like they actually care.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
Well what did it read for codes?
Did you run the self test to cycle the system?
There are bunch of funtional tests with a tech1 listed in the FSM.
Have you ever tried to activate the system on a dirt road or very wet/slippery one?
Could it be a short or failure of the indicator lights / electronics?
Did you run the self test to cycle the system?
There are bunch of funtional tests with a tech1 listed in the FSM.
Have you ever tried to activate the system on a dirt road or very wet/slippery one?
Could it be a short or failure of the indicator lights / electronics?
Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
Well what did it read for codes?
Did you run the self test to cycle the system?
There are bunch of funtional tests with a tech1 listed in the FSM.
Have you ever tried to activate the system on a dirt road or very wet/slippery one?
Could it be a short or failure of the indicator lights / electronics?
Did you run the self test to cycle the system?
There are bunch of funtional tests with a tech1 listed in the FSM.
Have you ever tried to activate the system on a dirt road or very wet/slippery one?
Could it be a short or failure of the indicator lights / electronics?
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
If it will not read any codes / connect to the ABS module and there are no blown fuses what can it be other than the ABS module? Do you have a FSM? Have you checked for power and ground at the ABS module etc.?
Instructor
Joined: May 2006
Posts: 106
Likes: 1
From: Greenbrier AR
The ABS is dead in my 91 and NOBODY has a clue as to what it might be.With as my of these cars there are out there I know Im not the only one that has had the ABS die.The system is the same from 86-91 I believe.I want to hear about all the problems people have had.I can fix it if I find the problem.Im not going to go through all the stuff Ive done but I will say it wont pull any TCs and wont communicate with any scanner Ive used,all I get is SERVICE ABS on the panel.Let hear what ya got.
Is the "BRAKE" light on? (Is your brake fluid topped off? On my '92, the fluid level sensor is way up there, so even a little low will kill ABS/ASR)
Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Sorry, but thats the way I see it.
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Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
[QUOTE=j Before talking to the service departments, and before you leave home, remove the chip on your shoulder, open your closed mind, and take off the defeatist attitude and put in the closet. Sorry, but thats the way I see it.[/QUOTE]
Dont waste my time with this bull$hit,you have nothing to offer here so do everybody a favor and -HELP- somebody else.You got nothing here so move on.
Sorry, but thats the way I see it.[/QUOTE]Dont waste my time with this bull$hit,you have nothing to offer here so do everybody a favor and -HELP- somebody else.You got nothing here so move on.
Advanced
Joined: Dec 2005
Posts: 52
Likes: 0
From: Jonesboro Ga
I had the same problem; Solution for me: Remove the ABS completely, connect the brake lines directly to the Master Cylinder. Problem solved. Please note that this was a decision I made based on the cost to replace the ABS unit. I do not advocate the modification of any factory designed system. I have two corvettes (1986 and 1987) and I cannot tell any difference in the braking. You make your own decision.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
If you would post what you have tested and the results it might make it easier to help you. I need to do some testing on mine as I do not get the self test everyone talks about the abs light blinks when I first drive after start-up I can not lock up the brakes with new rotors that got very thoughly cleaned and hawk hps pads and drm bias spring in a new master cylinder. It did go off once on a very wet road. There is plenty of brake dust on the front wheels and very little on the rears.
Can you get codes stored in every other device CCM C68 climate control Air bag ECU etc.?
Can you get codes stored in every other device CCM C68 climate control Air bag ECU etc.?
Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
If you would post what you have tested and the results it might make it easier to help you. I need to do some testing on mine as I do not get the self test everyone talks about the abs light blinks when I first drive after start-up I can not lock up the brakes with new rotors that got very thoughly cleaned and hawk hps pads and drm bias spring in a new master cylinder. It did go off once on a very wet road. There is plenty of brake dust on the front wheels and very little on the rears.
Can you get codes stored in every other device CCM C68 climate control Air bag ECU etc.?
Can you get codes stored in every other device CCM C68 climate control Air bag ECU etc.?
Intermediate
Joined: May 2010
Posts: 28
Likes: 0
Abs
I also have a 91 with non functional ABS. I have been so busy with other vette issues that I have yet to tackle ABS so I am very interested in what you find out. I have been disappointed in general with the braking, seems like there is no rear compared to my past sports cars. I appreciate the fact that you are trying to fix this yourself, which is what I thought this forum is about. Not how many times people tell you to go to dealer service. 2 cents.....
Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
Im getting close,I found an issue and should know something here pretty soon.The ABS in a ZR-1 is the same for all Corvettes.You would think with as many 86-91s out there it would be easier to find info.If I can fix this I can find the problem with the ABS.[IMG]
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Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
I have come to the conclusion these cars are not that complicated on paper but the way they are built service parts and test points are buried in impossible to get at places without major disassembly. An example would be if they put the ECM under the dash and relays and second fuse box there it would have saved a good deal of time later.
Thread Starter
Race Director
Joined: Dec 2003
Posts: 14,132
Likes: 935
From: Fremont Ca
2022 C4 of the Year Finalist - Modified
Hi David.When I removed the CDM box years ago I disconnected all the plugs in the area for easier removable.I found one of the pins in one of the plugs pushed out.Thanks again David for all your help on this.Theyre asking for your ABS knowledge over on the ZR1.NET site.