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Discussion Starter #1
2006, 2.4L, Sonata GLS, AT
~185K mi, started during snowy, wet winter
Original owner

The anti-lock braking system activates intermittently under lighter duty braking on dry surfaces. We can feel the ABS engaging through the pedal and hear it as the proper "rapid gurgling" sound. The activation might last a fraction of a second (a quick "berp") and occasionally up to just over a second, as a "berrrrrrrp." There's not enough effect on performance for it to pull to one side. The phenomenon goes away upon harder application of the brakes. On slippery surfaces the ABS works fine, seemingly as it should.

This false activation happens now at least two out of three attempts at braking and might happen two or three times for a fraction of a second during a single slow braking effort.

We drive the car in light duty traffic conditions almost exclusively. Hard braking from high speed is very rare. Pads look good still, calipers were rebuilt a couple years ago (~30K mi ago)

We're not getting the ABS malfunction indicator light nor any related codes. At least none taken from a common OBDII reader. Otherwise, we get a code that comes and goes about the evap system.

The ESP (electronic stability program, aka ESC) light flickers when I force it to activate on slick surfaces as a test.

I've removed, wiped clean, and reinstalled the factory front speed sensors and inspected the reluctor ring teeth for cracks, damage, or debris. All clean and clear. I haven't inspected the rear brakes yet.

Questions:
- How do we know which of the wheels are getting the false activation signals?
- What's the fix?
- Where are the ABS module and plugs for the sensor cables located? (2.4L AT)
- What are the proper Hyundai voltage and resistance tolerances when I check the sensors with a multimeter? And, maybe fabricate and insert breakout electrical wiring at the sensor connection?
- Where can I find explosion drawings of the various parts, that is, in relation to one another? I see online the ubiquitous line drawings of "Genuine Hyundai Parts," but they're only of individual parts themselves.
- Are the Amazon/Ebay/Alibaba <$35 sensors equivalent to the $100+ units from the stealer?
- Should I punt and go back to kraut mobiles?
 

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I've removed, wiped clean, and reinstalled the factory front speed sensors and inspected the reluctor ring teeth for cracks, damage, or debris. All clean and clear. I haven't inspected the rear brakes yet.
The symptoms your experiencing are usually caused by a cracked tone wheel (reluctor ring). Since you've already inspected the front two, the broken one must be on the rear.

How do we know which of the wheels are getting the false activation signals?
It'll be the one with the cracked tone wheel.

What's the fix?
Replace the cracked tone wheel.
 

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Discussion Starter #3
Your suggestions make sense, Autospark. Thank you. I'll be inspecting this weekend. Looks like new rear hubs with integral ring are about $45 to $100+ shipped from RockAuto.

I'll speculate that tone wheels/reluctor rings go bad from winter salt rust, and might also can degrade if the ring and hub are dissimilar metals. Maybe the rears fail more often than the front in winter salt locales, where the front wheels are cleaned by splash from puddles, while the rear end gets less spray.
 

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Karlello, what did you find as root cause? I am having the exact same issue with an Accent. we replaced alternator as mechanic saw low voltage to ABS system - nothing. had sticking front caliper and replaced it - nothing. Mechanic did not see any issue with front tone rings. watching speed sensors on scanner and they are all very close in speed. how did you find the root cause? Thanks!
 

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2006, 2.4L, Sonata GLS, AT
~185K mi, started during snowy, wet winter
Original owner

The anti-lock braking system activates intermittently under lighter duty braking on dry surfaces. We can feel the ABS engaging through the pedal and hear it as the proper "rapid gurgling" sound. The activation might last a fraction of a second (a quick "berp") and occasionally up to just over a second, as a "berrrrrrrp." There's not enough effect on performance for it to pull to one side. The phenomenon goes away upon harder application of the brakes. On slippery surfaces the ABS works fine, seemingly as it should.

This false activation happens now at least two out of three attempts at braking and might happen two or three times for a fraction of a second during a single slow braking effort.

We drive the car in light duty traffic conditions almost exclusively. Hard braking from high speed is very rare. Pads look good still, calipers were rebuilt a couple years ago (~30K mi ago)

We're not getting the ABS malfunction indicator light nor any related codes. At least none taken from a common OBDII reader. Otherwise, we get a code that comes and goes about the evap system.

The ESP (electronic stability program, aka ESC) light flickers when I force it to activate on slick surfaces as a test.

I've removed, wiped clean, and reinstalled the factory front speed sensors and inspected the reluctor ring teeth for cracks, damage, or debris. All clean and clear. I haven't inspected the rear brakes yet.

Questions:
- How do we know which of the wheels are getting the false activation signals?
- What's the fix?
- Where are the ABS module and plugs for the sensor cables located? (2.4L AT)
- What are the proper Hyundai voltage and resistance tolerances when I check the sensors with a multimeter? And, maybe fabricate and insert breakout electrical wiring at the sensor connection?
- Where can I find explosion drawings of the various parts, that is, in relation to one another? I see online the ubiquitous line drawings of "Genuine Hyundai Parts," but they're only of individual parts themselves.
- Are the Amazon/Ebay/Alibaba <$35 sensors equivalent to the $100+ units from the stealer?
- Should I punt and go back to kraut mobiles?
Cracked tone rings will USUALLY set a wheel speed sensor code. You are going about it the right way. Make sure there are NO leaks at any caliper.

Let us know what you find.
 

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Thanks. Which wheel was your issue and what failed? How did you finally find the problem? We are going on a month trying to locate root cause. Thanks for your help!
 

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Thanks. Which wheel was your issue and what failed? How did you finally find the problem? We are going on a month trying to locate root cause. Thanks for your help!

Did we scan the thing to see if module set DTC for an offending circuit fault to point you in some direction
 
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