ABS pump activating intermittently NO CODES! NOT AFFECTING BRAKE PERFORMANCE!

[Eric Wood]

Hi Eric and thanks for what you do. First and foremost THANK YOU! You help a lot of people, me included….You don’t need me to tell you how talented and appreciated you are so PLEASE let me tell you about one heck of a rare problem I seem to be having and you can let your talent, and experiene speak for itself.

I have became a fan of yours after buying (and now repairing) a 2010 Chevrolet Equinox ltz FWD (2.4 litre) in IMMACULATE condition. VERY well kept, and purchased from a good friend of mine. Vehicle has 110K on it and runs GREAT. After buying the vehicle I noticed it needed a bit of maintenance. Front and Rear brake pads, might as well do the front rotors as well while were at it…….Well apparently this is how you unleash your biggest nightmares, a pain int the a** worse than I’ve ever imagined…

So by simply replacing front and rear brake pads as well as the front rotors I now get an intermittent noise/vibration from the ABS pump…..Now the odd part, NO ABS codes, No check engine codes, no effect on the brakes whatsoever….They work fine! They work fine at all speeds….They work fine when I hear the ABS pump noise, They work fine when I DONT hear the ABS noise, TheABS noise can happen in ANY SITUATION when the vehicle is running…..EVEN IN PARK! It may happen once in a hour long, 50 mile drive or it may happen 75 times in an hour long, 50 mile drive. The noise happens at slow speeds, high speeds, mid speeds. It happens when it’s in just cranked up sometimes!

Now I can hear you experienced techs….You’ve been saying for my last two paragraphs “you back pushed the fluid didn’t you”? Dumb a**, you’ve got to do an automated bleed with a high end scan tool…………SORRY TO DISAPOINT, I’VE DONE IT….about 10 times to be exact. I will never call myself a parts swapper but desperate times call for…..(an email to EricTheCarGuy apparently) I’ve replaced parts….the front 2 sensors are new just because their readings on an ohm meter were a bit different than the rest (however their AC signal was beautiful…. I’ve also checked all electrical connections, I’ve cleaned plugs, I’ve scoped wires, I’m at my wits end…..

Ok, I’ll quit being sarcastic…..The problem is simple….VERY simple. An easy every day brake job has turned into the worst intermittent problem I’ve ever tackled. My wheel speed sensors are fine, their signal is fine, even replaced them after not believing myself…., the tone rings look great, the brake lines look great, the brakes have ALL been bleed OVER AND OVER manually and with the Autel auto bleed procedure. The master is fine, the booster is fine, the stupid electric vacuum backup motor is fine…….What ISN’T fine is listening to a loud vibrating ABS pump come on and off as it wishes when it wishes.

I am NOT a master mechanic by any means…..I’m a “good” shadetree with common sense, logic, and I know when to ask for help when I need it. …..Guys, I beg of you all…..what am I missing?

Without exagerating, I have spenty over 80 hours troubleshooting this problem…..if it’s a simple “try it” then I’ve probably already tried it….but hey, thats where you all come in. I’ve even pulled the EBCM connector off to look at the connections…..they look great!

There is only ONE THING that I can think of to mention that might hint at a clue for you seasoned guys……I will say that the “noise” does seem to happen more when it’s wet outside…..also when i got down and rolled my sleeves up micro managing this problem i used some very small brushes, almost like test tube type brushes to try to clean my tone rings……it seemed to slightly clear up a bit…..Well not clear up, but when the “noise” happened it didn’t seem nearly as intense or as frequent after cleaning the tone rings.

I’ve done a LOT of troubleshooting….I’m not a professional….I’m at the point where I’m about to order a new EBCM, New Hubs all the way around, and completely replace the ABS sensor’s wiring harness…..Thats the only way I feel I will solve this problem.

PLEASE……HELP ME!

Eric Wood, a grateful shadetree fella that works hard at the Shipping Port Of Wilmington NC to support his stay at home wife and awesome 5 year old son Christopher……I just can’t afford to pay someone to troubleshoot this insanely rare and touchy problem. I know these things take experts….it’s just not an option financially at the moment.

Thank you all so much in advance.

Topic

[Richard Kirshy]

Just a suggestion …
Have you tried reading live data ( wheel speed sensors and ABS ) during a road test drive while this is happening?

Beyond that…
Occam’s Razor says the simplest answer is often correct.
You may well have a faulty ABS unit

[Eric Wood]

Yes sir I have, the only difference I can get is rare and no more than about 1.5 miles per hour. 99% of the time they all read the same. I’m using a low end scan tool however for $50 it’s very impressive and it’s made by Autel….. Unless my refresh rate isn’t fast enough I’m definitely not getting any sensor’s completely dropping out or doing anything stupid that I can see. Thank you so much for your reply I hate to drop a couple $100 on a ABS module if I can’t find a used one. I’m definitely open to more suggestions for anyone that has time

[Richard Kirshy]

Interesting ….
Curious what other inputs besides the wheel speed sensors ( if any ) would signal the pump to engage.
Or if the command signal itself is corrupted causing the issue.
Or perhaps a varying or spiking voltage on the line.

Just thinking out loud here.

[Eric Wood]

I appreciate your thoughts… I assure you I am beyond puzzled myself. Hopefully more and more people will think out loud like yourself and maybe it might illuminate a light bulb on top of my head that leads to a solution (won’t be that bright). I promise everyone I will find the problem and report what ended up being the solution.

[Author]

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