HtownBlue

Situation and background:

2.5 YEARS AGO....Yes 2.5 YEARS AGO....in a far far land somewhere in Texas.....

I replaced my front bearings. During this procedure I obviously disconnected the entire front end including the ABS/Speed sensor on the front of the car.
Bearings eliminated the noise (whomp whomp whomp sound) issue I was having. But strangely another enemy entered my story. The day after I reassembled everything, I noticed something very odd.

When coming to a stop, while slowing down, and under 4 mph just as the vehicle was coming to stop the ABS WOULD ACTIVATE AND THE PEDDLE WOULD FLUCTUATE etc. The vehicle would come to stop of course normally, but the ABS would activate prematurely. It would flutter ONLY AT VERY LOW SPEEDS WHEN COMING TO A STOP, usually after driving at normal speeds such as coming to stop signs and lights.

Strange. So I take off speed sensors in front and clean them and make sure they are bolted on properly. Thinking this would solve problem.....but no. Still there.

So I thought maybe when I was disassembling the front hubs etc. I damaged the sensors. So I purchased NEW SENSORS and thought, bam, this will solve issue. NOPE. The enemy is still present and causing mayham.

So at this point I am at a loss. Not sure how to solve this issue. So I live with this inconvenience of the ABS consistently activated when coming to a stop but only at very slow speeds.

Finally after about 8 months I say screw it I will take it to the dealer to have them steal my money and tell me it was something stupid. So they check it out. They say sensors are all reporting data and that I have an issue with the ABS module. That makes zero sense because the ABS module is ONLY ACTIVATED WHEN THE SYSTEM TELLS IT TO. NOT TO MENTION THE ABS MODULE WOULD NOT BE WORKING AT ALL. OH mine was working all right. TOO OFTEN. And quite well. So I tell the dealer to screw off and they don't know what they are talking about. Enemy still plagues me for another 4 months.

After some research I discover that it could be the TONE RING which looks like a hollow gear on the axle that fluctuates the magnetic signal on the sensor. This "on and Off" fluctuation of the magnet on the speed sensor and how quickly it happens determines the speed reading. So it makes sense how this could somehow be the issue. That said, I have ZERO DESIRE TO REPLACE MY AXLES at the moment. That is a B*&^CH of a job.

4 more months go by. And guess what....the enemy is still there and as fate would have it I have to replace the axles due to CV clicking and vibration upon acceleration at high speeds.
F&*K!!! I do not want to do this job. Absolute nightmare of a job, but the bright side is that I would have BRAND NEW TONE RINGS ON BOTH FRONT AXLES. This will surely solve my abs/speed sensor problems! The Enemy will finally lose!
Except he didn't. After hours of pain removing the passenger side axle, and replacing, the new tone ring DOES NOTHING DIFFERENT. GRRRR..

Now I am stumped. another 4 months. Same garbage. Then I read that some parts manufactured in Asia for Lexus could have bad wiring in them. So I buy new sensors AGAIN. I knew I was wasting my money but hell, at this point I just want the damn thing working right. New sensors.....AND FAIL!!!! Nope. Still there.

So back to ANOTHER DEALER. They tell me that everything is normal and they cannot find out why it is doing what it is doing. They offer to so kindly replace my entire system for 2500 dollars. Oh how nice of them. They don't know how to fix it but will gladly take my money. Umm nope.

So now I am pissed. 4 months pass again. I read that I can buy a scanner system from China that will read nearly every sensor and system that Lexus has. It is only made in China because of licensing issues, but will read and communicate with my system almost identical to the 5000 dollar Lexus / Toyota Dealer Scan Computers. So I order it. But takes a while to get in.
2 months pass and it arrives. This machine is awesome. I can read data off almost every sensor in my vehicle and LIVE DATA AT THAT. I can read and erase ABS codes which standard scanners cannot do. I can read AC codes and sensors. This machine is legit!
That said I am able to pull up all 4 abs/speed sensors and view there live data. The actual readings they are giving out at that moment. So I go for a drive.....

Here is what I find. All 3 of my sensors are operating normally. My front right wheel however is not. As I approach 3.5 MPH or below it suddenly drops to 0. NO MPH while the others remain at 3...2....1 etc. as I decelerate.
SO I FOUND THE CAUSE. YAY right? Wrong. I have already replaced this sensor twice. I know I have a working sensor because it gives me readings at higher speeds.

WTH man!!!???? So from this point I hit the books. I read anything and everything about ABS sensors. You have active sensors and passive sensors. Active sensors read speeds at low MPH while passive usually do not read below 5 or 6 MPH. I'll save you the entire lessons. I learned a ton. I know exactly how these systems work and how they make the brakes fluctuate and flutter and why they do. All this knowledge but still no way to defeat my enemy.

Now I research some more. I find that some people have encountered similar issues in other vehicles when the sensor either became loose or for whatever reason was not mounted properly. But mine were mounted properly and tight. I promise. BUT......there is a reason that people would have that issue. These sensors can be very very sensitive. And if there is junk on the sensor, or if the sensor is out of place it will give off bad readings. Active sensors are even more sensitive.
So why is my sensor acting up? Well it turns out that the distance between the sensor and tone rings can effect output sensitivity. Maybe this is the issue.

But how on earth do I bolt the sensor closer to the tone ring on the axle when it bolts flat onto the knuckle housing? It has 1 10mm bolt that holds it in place while the sensor portion inserts into a hole that exposes the tone ring on the axle.
The only way to get the sensor closer to the tone ring is to manually file down the seating edge of the sensor where it contacts the knuckle. This will effectively make the sensor "longer" as the sensor will protrude through the hole further seeing as the the seated edge was filed down approximately 1 mm. Thus making the sensor 1mm longer.

So I take off sensor from knuckle. File down the entire seated edge along with the edge that goes around the cylindrical sensor portion. This in turn places the magnetic sensor closer to the tone ring. Bolt back in.

Hooked up fancy all knowing Chinese scanner and bring up all wheel abs sensors on my live data feed. Go for a drive. As I slow to stop at a light I watch the sensors. All 4 read: 6.......5........4.......waiting for abs activation.....BUT NO.......3......2.......1.......0!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

VICTORY!!!!!! I drive around in celebration trying to get the enemy to come back and show himself! NOPE. HE GONE!!!! And so is my ABS premature activation issue.

BOOOOOM!!!!! I win. HE loses. GAME OVER!!!!!

alchemist

iTrader: (1)

Wow man talk about diligence. Props to you

You know you could have called me and i would have walked you through everything you mentioned above in 10min

J/k

thomas1

Alchemist, you are too late I would have told him in 5 minutes.......

GWD

With that story and those problems it is a "SHE" not a "HE".

pauljcl

Congratulations! Well written, and, specially, evidence of an intelligent and persevering person. Bravo!

iluvny

Wow op, that's some story. Glad you finally solved it.

What was the brand and model # of your Chinese scanner ?

Also, I'm curious, based on your 2.5 yr ordeal, how the vehicle was able to pass safety inspections ? It never would here in NY. Ask me how I know that.

I had exactly the same symptoms as you and learned very quickly that the front sensors affect traction control.
When they get dirty and cause false readings, the symptom is as if you are trying to accelerate on ice from a stop and yellow, loss of traction icon in the dash.. Cleaning the front sensors solved that. The rear sensors affect the stop symptoms you describe..

Interesting that just 1mm affected your readings. In my case, it was a bunch of dirty filings on both sensors.

See my thread here from back in March : Click Here

Also, see this thread re ABS :Click Here

Photos in both threads.

HtownBlue

The brand of the scanner is Creader or Cread@r VII by Launch. I think that's the brand. That's what the box says.

The rear sensors were reading perfectly normal. I can read the live data on all 4 sensors and can see that all 3 of them were reading the exact same reading in MPH Down to the decimal point. All 3 would go as such : 4.7....3.8....3.3.....2.8.....2.1.......(.4)......0. The front right would read 0 well before the others.

You have a AWD which is slightly different than the FWD. I had replaced my rear hubs with the sensor in them already as well. You cannot clean the FWD rear sensors as the entire bearing and sensor is sealed I could of course press them out with my press, but no need. I replaced them in full.

The sensors can get dirty and cause lagged data sensing. The magnets on the sensors are specifically designed to get a specific magnetic electrical signal when each tooth of the tone ring passes below the magnetic sensor. This creates a specific on and off wave length with the passing of the teeth. When distance between the teeth and the sensor is increased, it effects the intensity and duration of the wave length. Thus causing the speed calculation to be off.

iluvny

Thanks for the info !

Yes, AWD the rear sensors are removable. ( I thought you had AWD as well ) However, they are NOT easily removable as the fronts. In fact, the Lexus and Toyota dealers near me won't remove them unless I agreed to pay for them if they broke. There's a design flaw in there somewhere

You didn't mention how your car was able to pass the Texas State inspection ?

Edit : LAUNCH Creader VII brings up over 100 results on Ebay. Pretty reasonably priced for what it does. As Will Smith said in Independence Day, " I got's to get me one of these"

HtownBlue

It passed inspection for the three years I had the issue. The ABS only activated when approaching 2-3 mph. And only for a half a second maybe. And the car stopped fine. No issues stopping. No code lights on as I cleared them when the issue first happened. I can clear ABS codes with the Creader.

iluvny

That's great ! Because, here in NY, any abnormality in the ABS system is a fail.

BTW, did you get the one vehicle Lexus specific Creader VII or the multi vehicle VII+ ?

HtownBlue

I got the multi vehicle scanner. I volunteer my time fixing vehicles for elderly and single parents that cannot afford it so I needed a scanner that could communicate with multiple vehicles.

Gs3500

Did this problem ever resurface? I'm facing the exact same issue and am prepared to try your solution. Any tips on how you file 1mm off the sensor?

fastnoypi

Clean the knuckle and sensor hole with sandpaper and wire brush before resorting to filing any part of the sensor.
The sensor should be able to just drop in without effort.

98GSOwner

Hello HtownBlue - Here is a huge Thank you!!!! I just got my '98 GS400 back from the shop where I had Bilstein HD shocks installed. The car had a weird ABS shudder just before stopping - it felt like the front. The mechanic said no codes had been triggered but his OBD tool showed the right front wheel had shown 0 MPH while the others were still at 3-4 MPH. He mentioned had put a wrench on the sensor attachment bolt to ensure all was tight as he was reassembling. It was late and I took the car home. We agreed I'd do some research and he'd be happy to work on it to get it fixed.

I found your thread with the answer! I pulled the right front wheel this evening and reset the ABS sensor closer to the rotor and retightened. This couldn't have moved it more than a 32nd of an inch..... Result: All fixed with no pain, no dollars spent, and no more down time! I realize you struggled for 2.5 years to find the answer. A big Thank you for all your efforts and for posting the entire story!! Your hard work has greatly benefitted me!! So interesting that it was even the same wheel that shared our issue. By the way, the Bilstein HD shocks are a very big improvement over the stock shocks with 106K miles on them. I'll post my assessment in the 2nd gen GS suspension section. Paul

shikbas

Once I had the problem with the ABS,,,,it turned to be one of the tone rings was bad,,there was a very small crack on it causing the sensor to misread