Need Advice on Possible ASR/ABS Problem

[bankboy]

Hi.

Found a '93. Car is absolutely gorgeous but there are a few possible problems so I thought I'd see if anyone could give me some input or advice.

Car drives perfect, EXCEPT there is some weirdness with brakes in a couple of ways.

1) Pedal pulses even when applied lightly. I was under the impression that you should not feel this unless the ABS was being activated due to a "panic" type stop.

2) There's some "grinding / chatter" type sound from the rear that occurs after you come to a stop and then take off again.

3) Both the ARS and ABS lights are lit up constantly. Based on what I've read, this seems to be a combined unit that controls both functions.

Also, only some of the functions work on the drivers power seat controls. No back and forth, no tilt. I’m guessing the motors are O.K., so does this sound like a switch problem?

I really like the car, and if not for these glitches it would probably be mine tonight, but I'd wanted to see if I'm looking at a major problem or something that can be corrected without some obscene amount of money.

Any advice would be greatly appreciated.

 

[-=Jeff=-]

See if you can take to to a mechanic to have the ASR/ABS checked out, I never had a problem but it could be a wheel sensor..

As for the Driver seat.. if it is a switch or the seat track it would be an easy fix. I would be more concerned on the ASR/ABS and have it checked if you can before purchasing the car

 

[c4cruiser]

Brake pedal pulsations may be due to warped rotors. Extreme braking can cause this. Have a shop check this out

The noise from the rear sounds like u-joints in one of the half-shafts or a rear wheel bearing.

The ABS/ASR system has a number of components that impact its operation. Cruise Control, throttle position sensor, wheel speed sensors, brake fluid level, brake condition, lateral accelormeter, even the tire size all play a part in the system operation. With the lights on both the ABS and the ASR systems are inoperable but the brakes will work.

The EBCM (Electronic Brake Controle Module) performs a self-test everytime the car is started and vehicle speed hits 4MPH. There is a soft buzzing sound that indicates the test is being performed. The ECBM can store error codes that can be read with a diagnostic code reader. Codes reported can be used to fix the problems. EBCM codes are read with the proper brake system cartridge installed in a Tech-1 scanner. EBCM codes can also be displayed through the CCM and displayed on the digital display area of the speedometer. The GM Service Manual has a description of ho to retrieve ABS/ASR codes thru the CCM.

Depending on how much you like this car, you may want to take it to a reputable shop for diagnosis of these problems. IF you do have a warped rotor that is causing the pedal pulsation, a complete brake job can run in the $700+ area. If you can do it yourself, the costs can drop a bunch. The ABS/ASR system can be very expensive to repair but that may depend on which part is causing the problem.

Do you hear any grinding noise when you try to move the seat in a specific direction? That is an indication of worn or broken gears that control a specific direction of movement. This a fairly common problem with Vette power seats. The switch could be the issue so that would be a good place to ckechk first. There is only 1 motor that controls movements so it sound like the motor is OK. The power tracks are no servicable so it's replaced as a unit. Figures $200 for a rebuilt unit from one of the Vette accessory catalogs like Mid-America Motorsports.

Sometimes the term "obscene amounts of money" and Corvette are used interchangebly You may want to keep looking simply because there are a lot of really nice cars available. I looked at 16 cars before I settled on the 92 vert I have!! Good Luck!!

 

[bankboy]

Your Excellent Feedback

Hi.
I'll do this in the order you addressed each issue.

1) The noise in the rear only occurs for a few seconds after you start to drive off and then goes away. Question... Coulld this be related to the E-Brake?

2) Is there a way to tell if the ASR control is actually turning it on and off? Tires are correct size, but good suggestion.

3) Didn't hear the buzzing you mentioned from the ECBM; don't know what significance this might have.

4) Would a warped Rotor cause these Indicator Lights to be triggered?

5) With regard to the seat, no grinding noise. In fact, no noise at all. What's weird is that a couple of the functions work, but for example seat won't go fore and aft...

6) I agree about the dollar aspect, but fun usualyy cost money...


Ron

 

[-=Jeff=-]

1) The noise in the rear only occurs for a few seconds after you start to drive off and then goes away. Question... Coulld this be related to the E-Brake?

When you say start to drive off, is this from every time you stop? or just when you first start the motor and begin to move. If it is when you first begin to move aftering starting then that noise it normal as it is the ABS doing a self-test.

 

[Hib Halverson]

1) Pedal pulses even when applied lightly. I was under the impression that you should not feel this unless the ABS was being activated due to a "panic" type stop.

2) There's some "grinding / chatter" type sound from the rear that occurs after you come to a stop and then take off again.

3) Both the ARS and ABS lights are lit up constantly. Based on what I've read, this seems to be a combined unit that controls both functions.

Also, only some of the functions work on the drivers power seat controls. No back and forth, no tilt. I’m guessing the motors are O.K., so does this sound like a switch problem?

Pedal pulsations without ABS operating indicates warped brake rotors, however, you say that the ABS Active and the ASR Active lights are on all the time. If it's on all the time then the ABS is working and you'll feel pedal pulsations any time it's active. Neither the ABS nor the ASR should be active all the time. Clearly there's a problem and perhaps an expensive one.

On the other hand, maybe it's the Service ABS and Service ASR lights that are on. If that's the case, you also have some problems with that.

You're statement that the car drives "perfect" is perhaps a bit optimistic. I would make an offer but contingent on the owner repairing the car, first.

 

[bankboy]

"Drives Perfect..."

Pedal pulsations without ABS operating indicates warped brake rotors, however, you say that the ABS Active and the ASR Active lights are on all the time. If it's on all the time then the ABS is working and you'll feel pedal pulsations any time it's active. Neither the ABS nor the ASR should be active all the time. Clearly there's a problem and perhaps an expensive one.

On the other hand, maybe it's the Service ABS and Service ASR lights that are on. If that's the case, you also have some problems with that.

You're statement that the car drives "perfect" is perhaps a bit optimistic. I would make an offer but contingent on the owner repairing the car, first.

By drives perfect I mean no clunks, no drift, car stops in straight line from 70 MPH with hands off of wheel. no shimmy, no shake; the car "feels" good.
But I do agree, something is definitely wrong, which is why I did this post in the hope of getting some feed-back or to see if anyone else has had this problem.

 

[c4cruiser]

Which messages doyou see lit up on the DIC??. Do you see the Service ASR and Service ABS warning or is it the ABS Active and ASR Active lights?

The "Service ASR or Service ABS lights indicate a problem with those systems. If the Active lights come on in certain driving situations, that means the system is working. The ASR and ABS Active lights should not be on constantly.

Also check the brake fluid level in the master cylinder resevoir. The fluid level must be at the indicator mark on the container (very close to the top).

You can test the ASR operation by simply applying full throttle from a stop. First, make sure that the ASR is on. By default when you start the car, the ASR On light should appear above the button (located above the headlamp switch). If you push the button, the light should go off. The light needs to be on for this test. Spinning the rear tires will activate the ASR system. You should feel a fairly strong pulsation in the gas pedal. The ASR system is automatically closing the throttle when the rear wheel speed sensors detects excessive speed compared to the front wheels. You should also see the "ASR ACTIVE" message on the DIC.

Find an untraveled road that is flat to test the ABS. From about 40-50MPH, apply full braking pressure and hold the brake pedal down. You should feel some pedal pulsation and the ABS ACTIVE message will appear on the DIC. If the wheels lock up and no light appears, the ABS is not working.

Try these steps and let us know what you found.

 

[bankboy]

When you say start to drive off, is this from every time you stop? or just when you first start the motor and begin to move. If it is when you first begin to move aftering starting then that noise it normal as it is the ABS doing a self-test.

Seems to happen fairly frequently after you take off from a start.

 

[spyysee]

check the rear bearings!
This happened to me; caused my abs to come on. the noise you hear is what may be
a failing rear wheel bearing.

 

[Skant]

I would not buy this car until the ABS/ASR problem is diagnosed/resolved by a proper mechanic. Many or even most of the issues that could cause this symptom are terribly expensive to repair. The symptoms you've mentioned may indicate serious problems with the drive train on this car. And these types of problems can easily turn into a long running expensive witch hunts trying to figure out which part is actually the culprit.

On the other hand, the problem could be something relatively cheap to fix (that meaning less than $1000).

Take it to a mechanic for a full inspection or walk away from it.


As for the power seat problems... these aren't so important. And they may be blown fuses and/or tripped circuit breakers. The various seat functions are split across a number of circuits. The main movements are on large circuit breakers. Check all that stuff out.

- Skant

 

[bankboy]

When Does Noise Occurr

When you say start to drive off, is this from every time you stop? or just when you first start the motor and begin to move. If it is when you first begin to move aftering starting then that noise it normal as it is the ABS doing a self-test.

Everytime. Not just when car is run for the first time on any given day.

 

[Zixxer]

It's like buying a house.....if you really like it and something isn't right, get the seller to offer a concession or have them fix it. I've really sunk a lot into my 96 after buying it for a great price off an auction but I would do it again based upon the fun factor and experience of working on the car.