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Virtual Technician
Virtual Technician, ASE Certified Technician
Category: Car
Satisfied Customers: 96
Experience:  25 years Experience. All makes and models, Shop Owner, Access to 4 repair databases. - I take the Opt Out Questions :)
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Occasionally when i be driving a hear like a small motor running

Customer Question

Occasionally when i be driving a hear like a small motor running noise and then the brake pedal starts to rise and get hard and when i push down on da brake it grinds to a stop ive replaced the brake booster/master cylinder, both front calipers,the brake pads are good and i replaced the driver side wheel hub and the ABS light remains on and still does the same the vehicle is a 1997 olds bravada
Submitted: 1 year ago.
Category: Car
Expert:  Virtual Technician replied 1 year ago.

Virtual Technician :

Hello, My name is XXXXX XXXXX I will try my best to help you with your vehicle issue. Just to make sure it is the ABS system doing this - have you tried pulling the fuse and test driving?

Virtual Technician :

Do you know what the ABS code is?

Virtual Technician :

Does it only do it when slowing down to a stop - say about the last 10-15 feet?

Virtual Technician, ASE Certified Technician
Category: Car
Satisfied Customers: 96
Experience: 25 years Experience. All makes and models, Shop Owner, Access to 4 repair databases. - I take the Opt Out Questions :)
Virtual Technician and 4 other Car Specialists are ready to help you
Expert:  Virtual Technician replied 1 year ago.

Our chat has ended, but you can still continue to ask me questions here until you are satisfied with your answer. Come back to this page to view our conversation and any other new information.

What happens now?

There were some standard questions that I needed to know.

I'll await your reply so that I may contine to help you.

Rich.

Customer: replied 1 year ago.
No i dont know what the abs code is and it happens (motor running sound) even when im not pushing the brake peddle but if i do apply the brake during the motor running sound the peddle is hard and it makes a grinding sound while stopping.the motor running sound lasts about 5-10 seconds and i havent removed the fuse and attempted to drive it
Expert:  Virtual Technician replied 1 year ago.

Does it when you are sitting still - that's a new one.

The ABS activates when it senses a different/slower AC signal from one of the sensors.

A scanner to know what the codes are would be helpful.

Does everything else on the vehicle operate properly?

Any warning lights on?

I ask these questions because if there is nothing else happening, we need to check some electrical wiring.

Do you have a multi meter?

Customer: replied 1 year ago.
The ABS warning light comes on when i hit a bump or something but goes back off a lil while afterwards as for it happening when im sitting still thats incorrect i said it happens even though im not applying the brake
Expert:  Virtual Technician replied 1 year ago.

1. My mistake - does it activate going any certain speed or mainly over bumps and such?

2. Does the issue ONLY occur when the ABS light is on or off?

3. Could you send me your VIN?

I want to look up your specific ABS system through GM.

4. When the motor is making noise & pedal is hard - does the brake pedal "pulse" up & down?

Thanks for the info - since I can't hear or feel it, I'm trying to narrow down the area.

5. Have you had the codes read - Autozone and places like that do it for free.

Customer: replied 1 year ago.
It activates at random now but before it only did it when i was making a right turn and applying the brakes when turning but now it does it more often and randomly.when the noise is happening there is some pulsating/vibrating from pedal i also recall that it never happens at high speeds only at maybe 20mph or less.someone mentioned the electro-hydraulic control unit as a possible problem but i dont know where that is located at under the hood nor is it available in any parts store i will send you vin # XXXXX a bit and swing by autozone to get a code reading.
Expert:  Virtual Technician replied 1 year ago.
#02-05-25-006B: ANTILOCK BRAKE (ABS) ACTIVATION AT LOW SPEEDS (CLEAN WHEEL SPEED SENSOR MOUNTING SURFACE) (JAN 5, 2006) Document ID#(NNN) NNN-NNNN/td>
Bulletin ID: 02-05-25-006B Release Date: 05-Jan-2006

Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)



Models: 1999-2000 Cadillac Escalade
1995-1999 Chevrolet Silverado (Old Style)
1995-2000 Chevrolet Suburban, Tahoe (Old Style)
1995-2003 Chevrolet Astro Van, Blazer, S10
1995-1999 GMC Sierra (Old Style)
1995-2000 GMC Yukon, Yukon XL (Old Style)
1995-2001 GMC Envoy, Jimmy
1995-2003 GMC Safari Van, Sonoma
1995-2001 Oldsmobile Bravada

This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes).


Condition

Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set.

Cause

The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.

Correction

Measure AC voltage and clean wheel speed sensor mounting surfaces.

  1. Raise the vehicle on a hoist.
  2. Disconnect both the front wheel speed sensor harness connectors.
  3. Place a DVM across the terminals of each sensor connector.
  4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's.
  5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor.
  6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service.
  7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBriteTM, or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion.
  8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor.
  9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218).
  10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor O-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037).
  11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub.
  12. Install the rotor, the caliper and the wheel.
  13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's.

Parts Information

Part Number

Description

89022217

(Canadian P/N 89022218)

(Package of 2 cans)

Rust Penetrating Lubricant

(Each can will service 50+ vehicles)

01051344

(Canadian P/N 993037)

(Package of 12 tubs)

Wheel Bearing Lubrication - Tub

(Each tub will service 25+ vehicles)

Place unused material on dealer shelf for future use.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

H9714*

Front Wheel Speed Sensor Inspect and Clean (Both Sides)

1.2 hrs

* This is a unique labor operation number for use only with this bulletin. This number will not be published in the Labor Time Guide.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

© Copyright General Motors Corporation. All Rights Reserved.


"Portions of materials contained herein have been reprinted with permission of General Motors Corporation, Service and Parts Operations" License Agreement #0410810.

Copyright 2007 - 2011 Service Repair Solutions, Inc.

~~~~~~~~~~~~~~~~~~~

This is what I am thinking but I would like to PROVE it :)











Customer: replied 1 year ago.
The vin number is. 1GHDT13W5V2724044
Expert:  Virtual Technician replied 1 year ago.

I'll follow up

Customer: replied 1 year ago.
Hey I removed the brake fuse this afternoon and it seems to have resolved the problem because it hasn't malfunctioned at all since then
Expert:  Virtual Technician replied 1 year ago.

OK - so it is definitely the ABS system causing the issue.

Did you understand the TSB I sent you? I know you did the one front hub - have you ever replaced the other front hub?

I did run your VIN and there are no recalls for it - but the previous TSB DOES apply to it. We need to start there to resolve the issue.

Customer: replied 1 year ago.
No I haven't replaced the other hub I know everything should be replaced in pairs but at the time I only could afford to do the front passenger you think that I should replace it also
Expert:  Virtual Technician replied 1 year ago.

Oh no - I own a shop and I NEVER recommend hubs in pairs - you do them as they fail. There are so many road conditions that come into play on individual hubs.

If you DO want ABS, I would recommend the repair procedure on BOTH front hubs.

 

It's kind of time consuming - it takes us about 2 hours to do them AND the possibility exists that the sensor is so corroded into the hub - it breaks - then YOU ARE left with the choice of a new sensor or replace the hub assembly.

We always perform the repair bulletin on new hubs that we install so we don't have the issue in the future.

 

 

If you can't afford it or don't care about ABS - leave the fuse out. -- QUESTION THOUGH-- with the fuse out, does your cruise control work - some vehicles it doesn't.

Customer: replied 1 year ago.
I haven't check to see if cruise control works but I did notice that the check engine light is lit up
Expert:  Virtual Technician replied 1 year ago.

Hmmm... computer is probably tied into the fuse somehow.

And THAT would be why we can't just leave the fuse out-- sighhhh....

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