1997 Avalon, Brake Flush, ABS Light On

[AnotherOldJeepGuy]

So a 97 Avalon is far from a Jeep anything, but the expertise on this site well exceeds limitation to Jeep.  About a month ago my son decided he would like to flush out his coolant and brake fluid since he really has no idea how old either might be.  Seemed reasonable to me so we proceeded.  I have done coolant flushing before, and although I have never done a full brake flush, I had bled brakes before.  Neither of these jobs have been problematic in the past.

 

Coolant flush went smooth.  Brake flush seems to be fine based on the fact that the brakes work.  But very soon after this flush the ABS light now comes on a lot.  It doesn't stay on and seems to come on sparatically, relatively close to using brakes.  And also the parking brake light does the same thing although not necessarily at the same time.

 

We are going to try bleeding again, since that's the only thing that was done between when the lights didn't come on and when they did.

 

The brake fluid add point is a small plastic reservoir, and we can only add very small amount of fluid at a time between bleeding cycles at each wheel.  We have been careful to make sure it doesn't go empty or close to empty.

 

Any insights?

 

Thanks

[Pete M]

any codes?

[Pete M]

wait, this isn't one of those times where you need to stomp hard on the pedal to reset a switch, is it?

[pizzaman09]

I don't know anything about the particular car, but my similar vintage 99 BMW M3 ABS pump had a bleeder screw on it.  It was practically undocumented but after bleeding it, it fixed my soft pedal and odd ABS performance.  Maybe the Avalon has something similar?

[gogmorgo]

I won’t pretend I’m familiar with the Avalon, or other Toyotas of the vintage. 
The “parking brake” light is also the brake failure warning light, and will come on if you don’t have fluid somewhere you should have it. Often there’s a level sensor on the reservoir cap. Sometimes there’s a switch sensing differential pressures between brake circuits. Sometimes an electrical fault that mimics the operation of the switch can turn the light on without a fluid or mechanical problem.

The abs light coming on would indicate a fault code. And it can be helpful to know what that is. Not all cheap code readers will read ABS codes, unfortunately. But some of the more common things to turn the light on can be quickly checked. Fluid level or leaks, bad wheel bearings causing erratic wheel speed readings, or seized calipers, for example. Maybe the brakes pull one direction or the other. But you’re kinda flying blind and guessing without knowing what the thing is complaining about. 
Something else a proper diagnostic scan tool can do is cycle the ABS pump to bleed it. This isn’t usually necessary but if air came in during the flush process it can get trapped inside the pump. You can sometimes get it to bleed out by using the brakes in a way that’ll activate the ABS, like a hard stop on a loose surface, but it’s not always effective.  

[AnotherOldJeepGuy]

17 hours ago, Pete M said:

any codes?

 

17 hours ago, Pete M said:

wait, this isn't one of those times where you need to stomp hard on the pedal to reset a switch, is it?

There was a speed sensor code of some kind but I don't have it handy, I'll read it again.  My reader isn't high tech enough to tell me which wheel :(.  I'll post back if the car makes it here today as potentially scheduled.  Still seems to be a standout that the original bleed was the only thing done before the problems came up, but who knows on a 97 especially.  Never hear of the "stomp hard reset"!

[AnotherOldJeepGuy]

13 hours ago, pizzaman09 said:

I don't know anything about the particular car, but my similar vintage 99 BMW M3 ABS pump had a bleeder screw on it.  It was practically undocumented but after bleeding it, it fixed my soft pedal and odd ABS performance.  Maybe the Avalon has something similar?

I'll take a look around the ABS unit...

[AnotherOldJeepGuy]

16 minutes ago, gogmorgo said:

I won’t pretend I’m familiar with the Avalon, or other Toyotas of the vintage. 
The “parking brake” light is also the brake failure warning light, and will come on if you don’t have fluid somewhere you should have it. Often there’s a level sensor on the reservoir cap. Sometimes there’s a switch sensing differential pressures between brake circuits. Sometimes an electrical fault that mimics the operation of the switch can turn the light on without a fluid or mechanical problem.

The abs light coming on would indicate a fault code. And it can be helpful to know what that is. Not all cheap code readers will read ABS codes, unfortunately. But some of the more common things to turn the light on can be quickly checked. Fluid level or leaks, bad wheel bearings causing erratic wheel speed readings, or seized calipers, for example. Maybe the brakes pull one direction or the other. But you’re kinda flying blind and guessing without knowing what the thing is complaining about. 
Something else a proper diagnostic scan tool can do is cycle the ABS pump to bleed it. This isn’t usually necessary but if air came in during the flush process it can get trapped inside the pump. You can sometimes get it to bleed out by using the brakes in a way that’ll activate the ABS, like a hard stop on a loose surface, but it’s not always effective.  

Yeah my reader is the low cost variety, just basic codes (see response to Pete above).  Sounds like the hard stop on loose surface may map to the "stomp hard" Pete was talking about.  Not a lot of gravel roads here in the city to simulate ice, it may be just as hard to find that as it is turning out to be finding the root cause!

[gogmorgo]

22 minutes ago, AnotherOldJeepGuy said:

Yeah my reader is the low cost variety, just basic codes (see response to Pete above).  Sounds like the hard stop on loose surface may map to the "stomp hard" Pete was talking about.  Not a lot of gravel roads here in the city to simulate ice, it may be just as hard to find that as it is turning out to be finding the root cause!

You might still get some abs action on pavement. Just be careful about it.

Speed sensor codes can be tricky. If it’s a circuit code it could easily be the sensor or wiring, but more often than not I find performance or erratic signal codes to be because of what it’s pointing at. Bad wheel bearings moving tone wheels around, tone wheels packing full of stuff or sections rusting away. Even rust jacking pushing perfectly good sensors away from perfectly good tone wheels. 

[AnotherOldJeepGuy]

23 minutes ago, gogmorgo said:

You might still get some abs action on pavement. Just be careful about it.

Speed sensor codes can be tricky. If it’s a circuit code it could easily be the sensor or wiring, but more often than not I find performance or erratic signal codes to be because of what it’s pointing at. Bad wheel bearings moving tone wheels around, tone wheels packing full of stuff or sections rusting away. Even rust jacking pushing perfectly good sensors away from perfectly good tone wheels. 

Well it is raining today, might be enough in the local closed school parking lot.  Not crazy about trying to trigger ABS but we'll see.  Planning to take a good look around the wheel sensor wires just in case something got bumped during the first flush.  Also hoping I can get to the wheel sensor connection and check the resistance at each to see if any stand out.

 

Any recommendation on a OBDII reader that is good enough to exercise the ABS and point to the real trigger?

[Pete M]

get a code reader that's bluetooth so you can use an app on your phone   

[AnotherOldJeepGuy]

I like that idea.  I have hunted around a bit but so far what I have found, Bluetooth or not, don't seem to fully support 1997 Avalon

[gogmorgo]

I think your best bet for affordability vs features would be finding a used professional tool. Like a Snap-on Solus or something.
Most modern professional diagnostic tools are just a Bluetooth dongle and software on a rugged tablet. But they’re not cheap. In theory the software is out there to run the same level of performance on a device you already have with a Bluetooth dongle but I’ve never done it.
Some parts stores will pull codes for you but I don’t know how in depth they’ll go. Sometimes with ABS stuff you want to watch sensor data as you’re driving and the parts store likely won’t do that for you.

[AnotherOldJeepGuy]

I was able to find on Toyota Nation how to read the ABS codes by putting a jumper across pins on the diagnostic port and watching the ABS dash light blink, and also how to reset ABS codes with that same jumper to see if any thing done is successful.  So I can start there without a meter.  Now if I can dig up some other secret method to cycle the ABS to bleed it, I'll be a step closer.

[AnotherOldJeepGuy]

Was able to read the ABS Blink Codes, said 3 of 4 wheel speed sensors were complaining.  Since I have a hard time believing 3 sensors just went bad simultaneously after working for 28 years, I opted for resetting the ABS codes (found a way to do this without a meter as well).  Also added some break fluid since it was setting just on the MIN mark and my son said the Brake light was coming on just when taking a long left turn.  Went on a 20 minute test drive, which included a visit to a vacant lot and getting in a bunch of long left turns, and slamming the breaks enough to get ABS to engage at least once, and so far, , no Brake or ABS lights.  I'll believe it is fixed after some time passes, but good for the first few minutes at least.

Edited January 2 by AnotherOldJeepGuy
grammer typos (removed)

[AnotherOldJeepGuy]

Some time has passed and adding brake fluid seems to have stopped the BRAKE light from coming on (knock on wood).  But the ABS light has come back on.  My son is supposed to be coming back by today to reread the ABS and see if the codes are the same, or different.

 

If the codes are different, and maybe even point to a single sensor we'll follow that lead.  Also intent to just do a good visual at each wheel to see if anything looks disturbed.

 

If however it once again show multiple sensors, any opinions on what might throw multiple wheel speed sensor codes?

 

Will post back on what code reading are now, same or different...

[gogmorgo]

Wheel bearings going out at more than one corner, tone wheels rusting and/or packed full of stuff... wiring issues maybe. Kinda depends on what the code is. If it's a circuit code then that would indicate a wiring issue, possibly a bad sensor. If it's an erratic signal it's more likely to be a mechanical issue.

[AnotherOldJeepGuy]

The codes on Jan 2 were 31, 33 and 34, the suspicious "3 of 4 sensors go bad at the same time" scenario.  The plan to recheck Friday fell through, so don't know if the same codes came back or not yet.  If my son's busy schedule finds an opening one plan is to reset these again and the drive around until the light comes back and stop and read it again to see if all three come back at the same time.  That plan would also include inspection to see if any thing looks disturbed visually.  Would be nice to have live data, but I still don't have any tool that will read that and most internet research seems to suggest I'd have to get a pretty expensive unit for it to read this particular car.  Seems like for Toyota you basically need a 21st century model for this for ABS info to be well supported.

 

[Pete M]

I wonder if there's a common wiring issue that can cause that.  

[gogmorgo]

“Signal malfunction” instead of a circuit code would tell me the sensors aren’t sending useful data, rather than a wiring problem. Meaning they’re not reading the tone wheels properly. That would be a bearing issue, sensor misalignment, tone wheel corrosion sort of concern. The sensors passed the circuit integrity checks but aren’t sending good signals. 

[AnotherOldJeepGuy]

39 minutes ago, Pete M said:

I wonder if there's a common wiring issue that can cause that.

Sure seems like it has to be a common "something"!

 

23 minutes ago, gogmorgo said:

The sensors passed the circuit integrity checks but aren’t sending good signals

Ah, I didn't think of it that way but I see what you are saying.

 

Any past experience with "negative logic"?  I still can't get past in my mind that 3 of 4 bearings, tone wheels, or fill in the blank, would all go out at the same time after all 4 being good since 1997!  So what I mean by negative logic here would be a problem with left front, the only one NOT failing, actually being the real cause?  Just wondering is anyone has actually seen such a condition....

[Pete M]

do the rears share a common ground that has become sketchy? 

[AnotherOldJeepGuy]

As soon as I get the chance I am going to look at everything I can see from underneath for anything suspicious.  If I don't see anything I am considering just disconnection what I can get to and cleaning it, and even try pulling and reinstalling the existing sensors, although if I can't get the sensors out easily I may not go to that step just yet.

 

Worth noting that once the codes are cleared it does take some time for the ABS light to fire again, it's not instant failure.

Edited January 20 by AnotherOldJeepGuy
typo, add some info

[gogmorgo]

I suppose something could be scrambled in the abs computer. 

 

If the sensors aren’t quite in alignment due to age or weathering, a hard manoeuvre of some kind might be just enough of push out of alignment to start registering issues. 
Bearings often end up getting replaced in sets, based on the logic that if one is gone then the rest aren’t far behind. I don’t fully believe in that logic, but if it holds it would stand to reason that failing bearings are happening around the same time. And unless there’s a seal or lubrication failure, you can get away with rolling on loose bearings a long time before something catastrophic happens.  The same everything happens equally to everything logic also applies to corrosion, dirt accumulation, anything else that could suddenly get to a tipping point. 

 

But we’re all just speculating here. 

I’ve experience cases where a lost signal makes the vehicle incorrectly think the wheel has stopped while braking, actuating the abs and releasing the brake on that corner, but you’d notice the pull and pedal pulsing.