KimShep7

I'm having a heck of time with this. Maybe someone has an idea.
Problem is that when slowing down, ABS activates when it shouldn't. Come up behind someone at a stop light, on dry ground, and ABS acuates.
Disconnect ABS connector at the pump, and car runs, brakes all just fine.
When put on ABS diagnostics tester, it shows rear brakes actuating ok.
Tester shows no front brake activation. I've replaced the ABS ECU. I replaced the deceleration sensor. Now I'm thinking I have to replace the ABS solenoid block. But I hate to keep chasing the problem with parts. There doesn't seem like much left to do. The car doesn't seem to see that the front brakes are working.
Have inspected and cleaned wheel rings and all seem ok.
Any ideas?

KimShep7

Sorry, this is my first post.
I have a 2001 RX300, 97,000 miles. In otherwise great condition. Driving in Maine.

bearbrew

Have you cleaned the sensor at each of the wheel rings? They can get a buildup on them and not work properly. There is a write up on the forum on checking and cleaning them.

KimShep7

Yes, I've been over and over the wheel sensors and they seem ok, and the wheel rings too.

Maybe there is an older thread on this subject that I can't find?

Are stuck solenoids common?
I don't suppose I could rebuild that block, or somehow free up the front ones, if indeed they are stuck and that's the possible problem.

KimShep7

and finally, yes I have read as many posts here as I can find. I just can't make it all make sense. The ABS is seeing BOTH front wheels with no reading. Its like I have no front brakes. But with ABS disconnected I have full 4 wheel braking just fine. If it was reluctor rings or something, I think it would be cooincidence that both front wheels went at the same time.
It keeps sending me back to ABS control system somehow. ABS ECU is not getting a signal that the wheels are turning or braking, on both front wheels, so it sees a difference in wheel speeds and activates ABS. Could it be a broken wire? Is there some common place to look?
Screwy, that's for sure.

maxSteel

look on lexus owners club in the how to's for the rx200 repair manual. There is a section on ABS diagnostics and how to read the abs trouble codes

KimShep7

Thanks for the idea. But the thing is that its not throwing off any trouble codes.
Everything seems to be working just like it is supposed to, except that the car is seeing that both front wheels are going a different speed than the rear wheels, so it correctly activates the abs.

Seems all sensors are working. I put in new ABS ECU, new deceleration sensor, cleaned everything... yet its seeing wrong values.

Damndest thing. I've read every word ever posted on it.... but, the mechanic and I are lost. I have a new ABS pump assy coming soon. I guess I'll swap that out and see what happens.

Fix by replacing parts.... what a terrible adventure.

bearbrew

Really a WILD thought, but check your tire sizes. There is a very remote possibility that the last time you bought new tires the installer may have inadvertently installed two different sizes.
Someone's frustration can lead others to all kinds of crazy thought!!!

KimShep7

yes, that's not such a crazy idea. When the mechanic first looked at the car, he was in a dark bay or something, and didn't read the tires sizes correctly, and came out and asked me why I had different sizes in the front and back.
Upon closer examination, we find that the 4 new tires are in fact the same size. At least that's what it says on the sidewall.

With the diagnositics hooked up. it still doesn't read any signal that the front solenoids are actuating at all. The tester shows when the solenoids actuate, and indeed he can actuate them manually while I drive the car slowly in a parking lot. So, I don't really know if they work correctly when I press the brakes, but the ABS system isn't seeing that they work.

Anyway, I've got a new ABS pump assy coming and will put that in and see.

Thanks for your thoughts.

bearbrew

Sorry none of us could point you in the right direction.

maxSteel

In my case one of the rings was slipping. You can feel it if you remove the sensor, put your finger in the hole, and try to rotate the ring.

Abs was coming on at low speed, no abs trouble codes reported.

cbones1979

This has been happening to me at low speeds around sharp turns. I slowly hit the break and I feel a pumping of the brakes. Just got inspected today at my local shop and they said their computer couldn't connect to read any ABS codes. I'd have to take it to a Lexus/Toyota dealer to read the codes.

All new rotors and pads on this one and this was happening before and after. Not sure if it is a big problem...what do you think?

maxSteel

Yeah, I think it's a problem when the breaks pump for no reason.
To make it stop I pulled my abs relay.

KimShep7

Well, my EBay ABS module came in. Now I'll put this on and see if it was the culpret.

I hate to "diagonose by replacing parts, but in this case I've not much other choice.

I'll advise if it works.

cbones1979

Yup

Pulled they relay and no pumping. Thanks