Like others said, most likely a wheel speed sensor. You'll need a scanner though to know which one.

This can also point towards a bad wheel bearing as well. Something to keep in mind.

quote:

Originally posted by Balzé Halzé:
This can also point towards a bad wheel bearing as well.

This can be true. However, you will typically hear or feel a bad bearing.

Well dang. I bought the Autoel AL629 obd2 tool. Hooked it up and seems like it works for everything but the ABS system.

I tried it on my GS and it all works, including ABS. So not sure if there is a tool issue with the ES or just with the tool itself. It couldn’t communicate with the ABS system whether the ABS light was on it off.

Maybe return the tool and buy a different brand?

Innova makes several units that can read fault and error codes for ABS modules. They're more than decent quality tools that don't cost an arm and a leg.

Strange (and maybe unfortunate) that there's no recorded code history when you had the car diagnosed at the auto parts store. Not sure about Lexus parts, but there should be some fault and error history stored someplace. 1999 isn't ancient times; EPROM chips were commonplace items on all sorts of circuit boards of the era, including car electronics. If a sensor is causing the warning light to light off, the ABS controller module should have a record of it stored in its memory. Shutting the car off should not reset that memory. Assuming that the store's reader is working correctly, I'd be more inclined to look at the controller as the possible cause; remember, the electronics in you Lexus is getting on two decades of age. Solid state circuits in regular use and in ideal environmental conditions still have a finite life; take into account the relatively harsh world that a car lives in, it should not be a surprise to anyone if the main control module is perhaps gasping its final breaths.

The good thing is that even if the controller goes completely kaput, the brake system should continue to operate fine, at least as fine as a non-ABS equipped car's braking system would operate. You just have to remember in a panic stop to pump the pedal to modulate the brakes, just like in olden days. Living in an ABS car for nearly 20 years will however cause people to forget (or even never learn) old, basic tenets that were once commonplace.

EDIT: I didn't read your last post before I posted. If the diagnostic reader you have isn't reading the ABS controller on your ES300 but works fine on your other car, I'm going to call it: you need a new controller module.

I just went through this for my ECU on my Porsche 993. My reader works fine on my other cars but couldn't get a proper read on the 911's computer. Some things were downloaded but other data was incomplete or were declared errors but unable to specify exactly what errors they actually were. Taking into account the car also felt down on power and idled in a crankier than usual kind of way, I more or less came to the conclusion that the ECU module was about to call it a life. 22 years isn't bad, but the $2300 for a new factory replacement module inevitably kinda stings. Still, not as bad as some ECU modules for rather commonplace M-B car models.

quote:

Originally posted by Balzé Halzé:
Like others said, most likely a wheel speed sensor. You'll need a scanner though to know which one.

This can also point towards a bad wheel bearing as well. Something to keep in mind.

Was going to say the same thing. I had a Honda Civic with the same ABS light issue. Also had a low pitched howl that got slightly louder as speed increased. Turned out to be a bad wheel bearing.

Thanks!

Yes, I find it odd that no history is kept - I'd want any block box function to keep a history of critical events like brake issues.

I tested my code reader on my other car and truck - it works fine for all functions, including ABS. So, it's just my luck that it's not working for the one function and for the one car where I need it to work.

I took the ES to the parts store again. The ABS light was on when I got there. But then they turned off the car to connect the their scanner (Bosch). They said the car needs to be off to connect. I said that the ABS light clears and then takes a 0.5-1 mile drive for it to appear again and asked if we could take a short drive to see if any codes appear when the ABS light turns on again. They said that their scanner doesn't work with the engine on. But their scanner, after turning the car off/on and reading the codes while the car engine is off is not showing any codes.

BTW, their scanner behavior is different. My scanner requires that the engine be on in order to read the ABS system.

So, the part shop scanner, while free, is not useful in this case. I'll try another part shop.


Let's say a scanner did work and could read the ABS codes while the engine is on and the light is on. What typically does the code indicate? That there is an issue with the ABS, perhaps localizing to a wheel? Or would it indicate what part might be bad (ie - sensor or magnetic or wheel bearing or controller ECU)?

Thanks guys!

Okay, took it to the shop. Handheld scanner didn't show any codes. Hooked up to a PC based tool, the scanner couldn't communicate with the ABS system.

They say typically this means that the sensor is shorted. If the sensor fails open, then typically the car throws an ABS code; not communicating suggests that there may be a sensor short.

I guess I'll keep the code reader I bought - seems to work in general and it's failing where other professional systems seems to failing as well.

I'll take it to the shop for them to walk all four corners to see which wheel(s) is failing and why. I guess I could do it w/ an DVM (if it's a sensor issue) but I don't really have a jack and stand yet. Still trying to figure out what to buy (in particular, how high do I need for the truck).

my old (2000) silverado (and many others' silverados) were known for ABS control module failure. symptoms were the same as yours.

I think lots of people are overplaying the 3rd party scanner issue. To be clear ODB2 does not include anything to do with the ABS system. The individual scanner mfg company is responsible for either reverse engineering or working with the mfg. go get those codes. With varying degrees of success. The larger brands they probably will cover, but an off brand not so much. And individual car companies can be more or less helpful. I would guess that Lexus will be one of the less helpful and low volume as well. I have a very expensive snapon scanner and a couple of other Mac ones and they simply will not tell me the bad sensor on a Subaru. My Subaru dealer can tell me instantly.
At this point I'd probably discuss having the Lexus guy read it. Or you could just start swapping parts depending on the relative costs.
You don't need any special jack or stands for this. The OEM jack to change a tire will allow you to get the wheel off and all these sensors are simply plugs near the brake system.

If the scanner cannot communicate to the ABS computer it is very possible the ABS module is being "shorted" by a faulty component. One way to isolate this would be to disconnect the sensors, either one at a time or all at once (depending on which way you want to work) and seeing if the unit comes online. You could also check to make sure the ABS module is getting input power when the vehicle is on. If you look at the ABS system it has a controller, solenoids to control brake pressure, and sensors to control the solenoid (roughly). I'm not an auto mechainc by trade but if I were troubleshooting no comm to a module I would start by making sure the module was recieveing power and if it was I would isolate the module from the rest of the system and see if I could talk to it. If I could I would suspect a harness or component that fed it. If not I would suspect the module. Troubleshooting is all about knowing how the system works and picking which end of your issue you want to start at. "If you know how it works, you know why it breaks".

A standard OBD scanner won't talk to anything but the engine. I use a Bluedriver scanner that talks to all of the vehicle modules. It's still only a one way scanner but for most repairs you don't require two way communication. Realistically a scanner just gives you a place to start your troubleshooting, it rarely gives you the answer.

I'm pretty sure you are way off base on this. In general no ABS that I know of is totally independent (i.e mere lack of power to the ABS will result in no ABS light). In addition no ABS that I know of will fail to light the ABS light merely for a sensor failure (its shorted the ABS module). That would pretty much be pointless from the mfg. point of view of determining the failing component. The sensors are low voltage components. The number one reason that you can't talk to the ABS module when there is not fault present (as is the case here) is your scanner is not set up to do so. ITs completely proprietary as to the type and nature of that communications.
FWIW>

Again, no auto mech but when I have had an ABS light and I scanned it it returned a failure code (usually a sensor). Easy to troubleshoot. As far as scanning it no it is not some special magic there are many scanners that can read them, and I have one. I scanned a friends Ford one day that had an ABS light. My scanner could not talk to his module, but it could talk to ABS modules in other Ford vehicles. Hmm. Wonder why. His module shit the bed, and basically set the light as a "the ABS computer is offline" message. For a lot of vehicles when the ABS sets a failure mode the system reverts back to old school hard brakes for safety reasons. The ABS turns off and sets the light. You query it and it returns a fault that it saw. If you cannot query it you need to see why it is offline. That can be a short, an open, or any number of things depending on the logic of that particular unit.

If he has an ABS light he has a fault present. That's why the light is on. The fault could be no comm to the ABS module, or it could be the module telling you it found something wrong. If you can talk to it it will give you a fault. If you cannot talk to it you need to make sure it is online. Pretty simple.

As far as low voltage sensors causing major issues....I have seen sensors that work on +/- 15 mvdc shut down entire systems when they go bad....

You make my EXACT point. Every system I know will report a code (via ECU or otherwise) when the ABS module is offline or otherwise not available. That is NOT the situation here. Trying to read the ABS module status when there is no fault detected (and no light on) and you cannot communicate with it (the reported problem) it is a scanner issue, not that the ABS module is offline or some other status. If it was offline the light would be on and you would get a code. As I stated above many scanners will not read low volume cars. That's just the way it is. Your scanner mfg. should indicate if it can read the vehicle you are attempting to address. These are proprietary codes. Reading Ford is totally common, reading Lexus or Mercedes not so much.

quote:

Trying to read the ABS module status when there is no fault detected (and no light on) and you cannot communicate with it (the reported problem) it is a scanner issue, not that the ABS module is offline or some other status.

Well no shit.

Here is a very general or loose guideline to ABS lights. If it comes on immediately after starting, stays on and never goes off, there is a "hard" failure of some kind, e.g., (most commonly), a wheel speed sensor that has no signal at all. If it is off at first but comes on after you get rolling a bit, it is often a sluggish or damaged wheel speed sensor or "tone ring." Did anybody do just a simple visual inspection on it? Maybe there is something obvious like a sensor wire jerked out by the roots or chewed by rats.

If a proper scan tool (costing thousands of dollars, not a sub-$100 "code reader" that doesn't even read ABS) won't communicate with the ABS, the module has most likely lost power or ground or is internally faulty.

Okay. The shop troubleshot the issue and their conclusion is the alternator is going bad and is putting out less voltage than required - 13v? This is leading to the intermittent ABS light issue. The brake system itself seems to be fine. So just need to replace the alternator.

Sound about right?

Either way if alt. is weak it must be changed, before something else fails. Don't know if it will correct abs light but change it.

Thanks -- yes, regardless if the alternator is going bad, I'll get it replaced.

I guess I'm curious why the degenerating alternator (is that a pun?) is manifesting itself as an ABS failure versus something more broad (battery, MIL/check engine, or other things). Car has 140K miles so maybe about time but not intuitive that the signal is ABS light. Is there something about analog that makes it more susceptible?

I'm not a mechanic but work in the electronics field. I have seen bad alternators and weak batteries cause all kinds of issues.

Batteries act as a filter to an extent and reduce any ripple coming from the alternator which can cause computers in other systems to do strange stuff. if the alternator is putting out a bunch of noisy DC voltage and or the battery is not filtering things properly, you might see issues like you describe.

I had a 2009 GMC Sierra. One morning it went haywire, and went into limp mode (reduced engine power).

Was almost to my destination, made it there, and when truck was restarted check engine light came on, but everything else was fine, and I made it back home.

Next day (below zero both days this happened) truck started up just fine, with check engine light still on. Headed to the shop to get it checked out and halfway there the truck just quit while going along at 55 MPH.

Had it towed the rest of the way to the shop, and they said I broke the record for most codes they've seen. Something like 170 different codes. They diagnosed as alternator based off a lot of them being low voltage codes. New alternator, and battery (both were original) and truck was good to go again.

I was really surprised with a bad alternator that I didn't first get the hard start especially in the extreme cold weather.

Another thing of note. About a week before this I noticed an electrical burning smell. Not strong enough that I became concerned, almost so faint I thought I was imagining it, or it was atmospheric and just smelled it in the truck. Mentioned this to the mechanic, and he said that's a sure sign of an alternator going and said he could smell mine as soon as he popped the hood.