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Super Mechanic
Super Mechanic, Master technician
Category: Chevy
Satisfied Customers: 17218
Experience:  29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
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2001 Chevy Blazer: ABS light and brake light come on and go..stays

This answer was rated:

2001 Chevy Blazer Extreme. ABS light and brake light come on and go off as driving. Some days it does not come on and other days it stays on. Any suggestions?

Hello and welcome to Just, Super mechanic here. About your vehicle.


You will want to have it scanned for any trouble codes to see what area the problem may be in. Just let us know what the code(s) are and we can go from there.

Customer: replied 8 years ago.
That is what I was affraid you were going to say. Just to get it scanned they say it will be $60.
Whoa! I am not sure about Autozone, I know they can read engine codes. Either that or maybe a tire center that might just tell yo the code, (for free, or a little tip) ???
Customer: replied 8 years ago.
OH I was referring to the dealership. Did not think of autozone.
Most times the "stealership" will be more for most things. Wink
Customer: replied 8 years ago.
My son is taking it to Autozone now. Will get you the codes.
Customer: replied 8 years ago.
This is not going to be easy the only error that was in the system was cylinder 4 misfire. And that error was only in there once. The ABS light was on when the reading was taken. Got to be a sensor loose or something. Maybe a wire?

The only thing that I can figure is that it may be that the ABS is activating at low speeds, as there is a bulletin that mentions that with no trouble codes. Wheel speed sensors, dirty.


Bulletin No.: 02-05-25-006B

Date: January 05, 2006


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


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).


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.


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.


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, ScotchBrite(TM) 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 0-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.



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