Is it possible to disable the ABS unit, particularly on an 86?
Obviously, I would still like to have the brakes function! But I want the ABS unit to not be able to engage.
Disconnect a wire pack/plug in the module behind the seat perhaps?
And if it can be done, will the Anti-Lock light on the dash come on or not?

Why do I want to do this?
Well, there is some kind of problem with the ABS unit in the car. The Anti-Lock light comes on, and the ABS unit is ALWAYS engaging when you are braking and the car is between 5-10 MPH.
So, everytime I come to a stop, as soon as the car drops below 10 or so MPH, the ABS engages, until the speed gets below 5MPH.

I have taken the car to over 10 Chevrolet dealerships, and none of them can diagnose the problem, because none of them have, or can obtain, some magical testing tools. There are 2 tools necessary to diagnose the ABS system (I have the part numbers at home, and the page from the assembly manual). Anyway, GM must have only made 1 of each of these tools, because they are imposibble to find.
Without the tester, we can not determine what is wrong with the system. We could just replace the ABS module and all of the wheel sensors, but with parts and labor, that will be hundreds of dollars, if not more. And then, there is no guarantee that would fix it, as it could be a wiring problem. (Isn't there also some type of lateral accelerometer deep in the dash board too?)

So, unless I can someday find a dealership that has the proper tools, we are left with 2 options: disable the ABS system, so it isn't constantly activating and thus screwing up the rotors, pads, and who knows what else. Or, never drive the car again. :( I guess a third option would be to burn it for insurance money! :reddevil :jester

But seriously, if anyone here could either tell me how to disable the ABS system and the Anti-Lock dash light, I don't mind driving the car with out ABS. Our Stingrays don't have ABS. :D

Or if anyone knows of a dealership that deals with C4s A LOT, and might actually have the mystery tools, I would be willing to call them, and if they are not within driving distance, perhaps work out someway to pay to borrow the tools to diagnose my problem.

 

Did you try removing and cleaning the metallic dust/dust off the wheel speed sensors?

After I did that on my 93, the ABS system quit coming on as randomly as it used to.

I support you in your quest. It is no secret that locked-wheel braking usually provides shorter straightline stopping distances in dry conditions than ABS.

 

What did you clean them with? Just water, or did you use something like WD40 or something else?

As for the part numbers that I mentioned in my original post, they are:

Tester - J35890
Pin-out Box - J35592
These are listed on page 5E4 in the manual.


BTW, we did talk to Gordon Killebrew about this problem last fall, and he gave us a set of instructions to test the wheel sensors without the listed tools. It involved getting the car up to 15MPH, and measure resistance and voltage of the wires leading to the module behind the driver's seat.
Everything in that testing scenario tested successfully. But, that still leaves the ABS module, wiring, and if there is a lateral acceleromoter. Also, it only means the wheel sensors are working properly if we conducted the test that Gordon gave us correctly! Always a possibility for human error. :bb

Any thoughts or suggestions are appreciated. :)

 

Its 125 miles from Harrisonburg to McLean but I believe that Koon's Chevrolet have the equipment you are talking about. One of the best vette mechanics around here is Joe Malo. http://www.koons.com/joemalo/joe.htm It might be worth your time to give him a call or send him an email.

 

To answer your question about diabling the ABS though...

You can pull the fuse but be careful testing it. If you have upgraded to the 13 inch brakes or put in a brake bias spring, it is Real easy to flat spot a set of tires. Not to mention having anyone following you end up in the back glass.

 

Do you know what fuse to pull? Is it located in the fuse box on the side of the dash when you open the passanger side door? Will pulling the fuse you are talking about disable the ABS and turn off the DIC light?

The rotors are the stock ones (although it is a Z51, so they are larger, but not like Zr1/GS brakes), and the bias spring has not been changed.

 

Thanks, I will give them a call.
Honestly, if they have the right tools and skilled people, I don't consider 125 miles too far to go to resolve this issue that has been preventing us from driving the car since last August or so. :(

Thanks again for the contact info. :cheers:

 

Yes it's in the fuse box. I don't remember which fuse off the top of my head. It was listed in the owner's manual or the GM shop manual, can't remember. I'll have to look and get back to you.

It disables the ABS completely. I don't remember the DIC light, but I think it stays off also.

 

Sounds like you have one wheel speed sensor signal that is dropping out early during low speed deceleration. The ABS sees the signal dropout as a locking wheel and activates.

The signal strength of an inductive wheel speed sensor is a function of velocity as well as the airgap between the sensor and the toothed ring. If the airgap is increased too much (due to worn-out bearings, etc.) the signal can dropout within the ABS functional limits and cause an activation. To test accurately an oscilloscope should be used. Find a way to spin each wheel while measuring the sensor signal. You want to compare the signal output in terms of mv/hz or the amplitude in mv divided by the frequency in hz. 3-40 mv/hz is reasonable. If one sensor is much lower than the others this is your problem.

 

Good luck. I chased a mysterious ABS "not working" (rear wheels locking) problem in my '89 for months. Wheel sensors checked OK. But, so did everything else! So, I finally bought everything from wrecked car and replaced the pump, all relays, control module, & lateral acceleration switch. Bingo, it worked! BTW, Lateral Acceleration Switch is under/behind the radio. Good Luck, Paul :flag

 

Well, I pulled the fuse, and the ABS does not activate anymore. :hurray:
Only problem now is that the DIC light for "Anti-Lock" is always on. Any ideas on killing that light?

Thanks. :cheers:

 

Nothing off the top of my head except take the center off and remove the light for it. I've never had mine off so I'm not sure how involved it is. Sorry I couldn't be more helpful.

 

Thanks. I had thought of that, but I can't remember from when I had the bezel off to replace the radio if the DIC panel face can then be removed to get to the bulbs.
If not, I was thinking there has to be a wire than runs to that light from somewhere. ECM maybe?
If anyone has any thoughts, let me know.
If I don't get anything else before this weekend, I will start with removing the bezel and seeing if I can get to the DIC bulbs from there.

 

Once you get the center bezel off, you can remove the DIC section and remove the bulb, easy fix.

 

:hurray:

Thanks for the info. I will be trying it this weekend, and I'll let you all know how it goes. :thumbs:

 

You can unplug a connector in the ABS box behind the seat to kill the light (on my 89). Cant remember which, but it is a wire to wire connector, about 4 pins. My ABS is screwed too, (although mine just never comes on), and I pulled this plug so that the goverment annual test guy wouldn't know ABS was fitted. If it is fitted it has to work :eek: