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Hodgdon Extreme
Hsvracing Member


Age: 39
Joined: Mon Oct 26 2015
Posts: 180

Automobile: IS300


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PostPosted: Fri Jan 11, 2019 1:59 pm  Post subject:  Diagnosing ABS system malfunction Reply with quoteBottom of PageBack to top

So ABS system started occasionally activating when I was gently *just* about fully stopped. It started doing this more and more often, and eventually, every time I came to a stop. But only a gentle stop.

Read up on it a bit online and learned it was a common problem with the IS300, because trash gets between the tone/reluctor/toothed ring on the rear stub axle and the tip of the ABS sensor.

Bought a code scanner capable of monitoring ABS and checked it out. The update rate on wheel speed is slow, but the rear left wheel signal seemed to be dropping to zero a bit prematurely when lightly braking coming to a stop...

Pulled my ABS sensors to inspect - found the teeth on the rear left tone ring to be all chewed up, yet tip of sensor looks great??? WTF

Said fuck it and pulled ABS fuse for awhile. Then got motivated to fix...

So the tone ring is pressed onto the outer diameter of the outboard CV housing of the axle, non-replaceable. Bought a good used one on ebay.

Upon installation, I discovered that Lexus installs a stainless steel ring insert (made of ~.025" thick sheetmetal) into the upright, to surround the tone ring on the CV housing. Water/salt gets between the stainless insert and the steel upright and causes the upright to rust. That rust pushes on the stainless insert enough to cause the tone ring to rub on it - thus chewing up the teeth on the tone ring...

So I start grinding on the stainless insert to create clearance and realize there is enough rusty delamination in there that grinding is a lost cause, so I just remove the stainless insert all together.

I inspect the other side and it's almost as bad. So I pull it apart, remove the stainless insert and grind out the rust.

Reinstall the ABS fuse and test drive - problem is worse than before! Now the ABS activates at speeds as high as ~20mph, under light OR moderate braking. Not every time, but pretty often.

Monitoring individual wheel speeds on my scanner, they all appear to work great. I am getting multiple trouble codes to include:

Right Rear ABS circuit fault, Left Rear ABS circuit fault, Right Rear foreign object stuck to sensor, Left Rear foreign object stuck to sensor, ABS system malfunction

Inspecting my ABS sensors, they look great - nothing stuck to them. The wheel speeds always look good on the scanner. The ABS light on my dash comes and goes from one drive to the next (when light comes on, the system is totally deactivated).

My only thought is the stainless rings I removed had an important function, but I'm not smart enough to figure out what. I can ebay some replacement uprights that aren't rusty, but I'm not that confident it'll fix the problem.

Thoughts/ideas?


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maireeka
I absolutely have no life


Age: 31
Joined: Tue Dec 18 2007
Posts: 5927
Location: Little Hartselle Town
Automobile: Miata


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PostPosted: Fri Jan 11, 2019 2:05 pm  Post subject:  (No subject) Reply with quoteBottom of PageBack to top

My first inclination is the stainless rings had a function that you aren't aware of (same thought you have had). Can you just make some new ones?

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jrsy91gmc
Hsvracing Member


Age: 38
Joined: Thu Jun 23 2005
Posts: 450
Location: Athens
Automobile: couple


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PostPosted: Fri Jan 11, 2019 2:57 pm  Post subject:  (No subject) Reply with quoteBottom of PageBack to top

Are the stainless inserts you removed magnetic?

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Hodgdon Extreme
Hsvracing Member


Age: 39
Joined: Mon Oct 26 2015
Posts: 180

Automobile: IS300


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PostPosted: Fri Jan 11, 2019 3:45 pm  Post subject:  (No subject) Reply with quoteBottom of PageBack to top

maireeka wrote:
My first inclination is the stainless rings had a function that you aren't aware of (same thought you have had). Can you just make some new ones?


If it were a Duesenberg I was restoring, yes - I could make new ones...

But it would be easier to buy some replacement rear uprights that didn't live in New Jersey and Missouri for 10 years, collecting salt all the while.

jrsy91gmc wrote:
Are the stainless inserts you removed magnetic?


No. I was thinking maybe they act as some kind of magnetic flux shield or something, but being pressed into a 10lb hunk of steel seems like it wouldn't matter?

The insert itself was a ring about 3" in diameter, 3/4" long, and .025" thick. It had a hole through the outer diameter about 1/2" diameter that allowed the tip of the ABS sensor to poke thru.


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wtfmarine
Jr. Postwhore


Age: 39
Joined: Sat Aug 31 2013
Posts: 732
Location: Hsv
Automobile: 2007 335i; 79 Chevy K20
1/8 mile: 6.9@Your Moms
1/4 mile: ran out of tire :/
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PostPosted: Sun Jan 13, 2019 9:01 am  Post subject:  (No subject) Reply with quoteBottom of PageBack to top

Pull the ABS fuse again lol.

The stainless rings could be something for resonance, protecting the sensor from the rust, or who knows what. Probably was a bandaid fix after the original design and toyota decided it was cheaper to eat sensors vs a new design.

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