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I have a 2001 gmc sierra and I replaced the bearing on the passenger side because I had noticed that when having my wheels turned my brakes would pulsate when turning. Once I had replaced that the pulsating went away. Now I have changed my drivers side bearing because I had felt the same pulsating in my brakes. I have done the bearing test by shaking the wheel and it moved around so I went on and changed the bearing out. Today I have felt the same pulsating brakes. After my browsing on the internet I have the impression. That it may be a ABS sensor? Anyone have some info or have run into the same problem?
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Any time you have brake pulsating the first thing to look for in my opinion would be for warped brake rotors for the front…(rear if it has rear disc) Or warped out of round drums.
Quick way to tell which, front or back. Go down the road and gently apply the parking brake. If you feel the pulsation? The chances are high the issue is with the back brakes. (That’s where the parking brake cable does it’s thing)
If you do not feel it? Then gently apply the brakes and see if the steering wheel gets the “Wiggles” or “Pulsation”. That would point to a warped brake rotor. Keeping in mind brake rotors warp for mainly one big reason. Brake Caliper not doing it’s job correctly. Hanging up on the slides/pins. Sticky seal not allowing the piston to retract correctly. Once you figure out front or rear? You can in most cases put the front/rear up on jack stands (safety first) and spin the tire(s) Most likely you will hear and see the problem as the brake will drag and catch on the high spots.
Now if we are talking about brake pedal pulsation due to the ABS system? Sensor inop or damaged..Always worth checking the grounds to the ABS unit/controller. Any lights on the dash giving clues? It might be worthwhile to have the truck scanned for codes. Many of these onboard systems can point the tech/owner to some very nice data on what to look for.
Hope this info was in some way helpful. I’m sure others that may have run into these same issues will also chime in.
S-
Just for conversation sake. suppose the rotors/drums/ bearings check out fine. Although this would definitely set an ABS code, would unplugging the wheel speed sensors then driving a safe distance, confirm or rule out an issue with the ABS system. like said just asking for conversation sake. I don’t know weather this would do anything or not.
I can’t say what effect, if any it would have. I know with the older systems bad grounds could create a lot of headache and trigger abs warning/malfunction lights. It might be easier for this user to–if he suspects an ABS error– To see if perhaps an OBD II scan tool might be able to access that module to see if there are any set or pending codes that would offer direction.
I’m fairly decent at normal brake systems, but I’ve not turned a wrench professionally in a while, so even the 2001 beetle I’m driving while my bronco is sidelined? I’m learning A LOT about the newer systems.
S-
There should be a fuse you can pull to kill the abs, at least that’s true for my car.
I once had on ceramic brake pads – good for little or no dust. Well, if I exercised the brakes in a hard stop pad material would transfer to the rotor. This caused more of a shake in the steering wheel than a pulsation of the pedal but there was some of that too. As you drove on this would slowly go away. Anyway, I got some different pads and the problem was fixed.
The first thing to check with a brake pulsation like that would be the rotors, not the bearings. In fact, here’s how.
More info here.
http://www.ericthecarguy.com/faq/solving-brake-problems
Good luck and keep us posted.
Hey everyone sorry it has taken me so long to get back I wasn’t getting anything to my phone. So I have ruled out it being my brake system it is my abs. I have pulled the fuse because it is an older truck and I don’t want pay for the new ABS system. But now with the pulled fuse my abs light and my parking brake light remains on. Is there a way to get them off or is it something I need to deal with.
Thanks!
ChadRemoving the ABS fuse will put your truck back to base brake system and the lights will stay on and they get hot.
I’ve seen the low speed ABS activation caused by various things on that truck; most caused by: corrosion between the mating surfaces of the ABS sensor(s) and the front brake hub, and worn front wheel bearings. Probably the most common is the corrosion problems.
I’m not going to preach on “possible legal issues”, but repair your ABS system; I would pull the wheels,rotors and clean the sensors.
If I remember, disabling your ABS on that truck will also disable the DRP, which could/will cause premature rear wheel lock up. The dynamic rear proportioning (DRP) is a control system that replaces the hydraulic proportioning function of the mechanical proportioning valve in the base brake system. The DRP control system is part of the operating software in the EBCM. The DRP uses active control with the existing ABS in order to regulate the vehicle’s rear brake pressure
Remember safety first!
I never looked at it that way. Thank you. The two sensors are new. The one sensor is two weeks old and the other one is a years old. Is it possible for it to the much corrosion on it or should I be looking in another spot?
ChadChad,
If you drove on treated roads this winter, the year old one maybe the issue…if not more diagnosis…hopefully I can help.Chad,
I found my factory training book and also a TSB about the slow speed ABS activation and some specs for testing. If you have no EBCM codes and slow speed ABS activation you would do this… Remove the front wheel ABS sensor(s), remove the front wheel ABS connector(s)above the front suspension shock tower, measure the ohms of resistances of the front wheel ABS sensors and you should have around 1040-1050 ohms. Perform the recall, (put the sensor back into the hub) check for voltage output at the front wheel ABS connector by spinning the wheel one revaluation per second. You should get at least 350 mV (AC)Hope this helps…I’m going to be gone for a couple of days…please post your results
Recall Date:
AUG 29, 2005
Model Affected:
2001 GMC Sierra
Summary:
CERTAIN PICKUP TRUCKS AND SPORT UTILITY VEHICLES MAY EXPERIENCE UNWANTED ANTILOCK BRAKE SYSTEM (ABS) ACTIVATION. THIS CONDITION IS MORE LIKELY TO OCCUR IN ENVIRONMENTALLY CORROSIVE AREAS. THIS RECALL WILL BE LAUNCHED IN THE “SALT BELT” STATES OF CONNECTICUT, DELAWARE, ILLINOIS, INDIANA, IOWA, MARYLAND, MASSACHUSETTS, MAINE, MICHIGAN, MINNESOTA, MISSOURI, NEW HAMPSHIRE, NEW JERSEY, NEW YORK, OHIO, PENNSYLVANIA, RHODE ISLAND, VERMONT, WEST VIRGINIA, WISCONSIN AND THE DISTRICT OF COLUMBIA ONLY.
Consequences:
THIS CAN CAUSE INCREASED STOPPING DISTANCES DURING LOW-SPEED BRAKE APPLICATIONS, WHICH COULD RESULT IN A CRASH.
Remedy:
DEALERS ARE TO REMOVE THE WHEEL SPEED SENSOR AND THOROUGHLY CLEAN THE WHEEL SPEED SENSOR MOUNTING SURFACE ON THE BEARING, APPLY RUST INHIBITOR TO THE CLEANED SURFACE, GREASE THE MOUNTING SURFACE, REINSTALL THE WHEEL SPEED SENSOR, AND CHECK THE PEAK-TO-PEAK OUTPUT VOLTAGE TO ENSURE THE WHEEL SPEED SIGNAL IS WITHIN SPECIFICATIONS. THE RECALL BEGAN SEPTEMBER 22, 2005. OWNERS MAY CONTACT CHEVROLET AT 1-800-630-2438 OR GMC AT 1-866-996-9463.If you pulled the ABS fuse and the pulsation went away, then it’s likely that was the issue. That said, you base braking system should still work fine. Since you pulled the fuse, the lights will remain on however. You might try the above suggestion to see if that was the issue. You might also check for codes just to be sure something isn’t stored that could point you in the right direction. I’ve added more info on ABS to this article recently.
http://www.ericthecarguy.com/faq/solving-brake-problems
Good luck and keep us posted.
thanks guys for the help.
i have found a bad ground on my ABS module. I checked the all the sensors and the installation of everything everything checked out.It is all fixed.
Thanks alot
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