Occasional ABS “burp” on my Celica

[Ross365]

I own a 2002 (Gen7) Celica, which is low mileage and generally in good condition. Just recently, I’ve started hearing what I’m sure is “ABS noise”, which just kicks in for a few seconds when I’m moving at very low speed (e.g. in car parks). It feeds back through the brake pedal too.

It’s been suggested to me that it could be a reluctor ring that sits underneath the sensor that has broken (apparently they rust and snap). Initial enquires suggest these cannot be obtained separately so it will be a new CV joint at ~£50. I’ve not had time to take a close look at it yet and I’m using my other car at the moment.
Can anyone offer any advice on this?

Thanks.

 

[The_Yellow_Ardvark]

The rings can snap or fill up with crud.

take a look at each wheel.

Plus each sensor plug.

 

[Ubique]

ABS generally isn't active at low speed, most vehicles need to be above 12mph for it to work (3mph for Landrover) Audi's suffer the symptoms you describe if there is air trapped in the ABS modulator - not enough to give a spongy brake pedal though. If you have any plug-in diagnostics, read the live values from the wheel speed sensors in the speed range you're having trouble in. Also check the wheel bearings for free play and the steering angle sensor calibration. Some vehicles also flash the ABS amber indicator when it kicks in - not sure if that applies to your vehicle though.

 

[m_c]

Anything I've worked on, the ABS has worked at low speed.

A cracked ring will give those symptoms, and it won't always be caught in live data.
If the split is bad enough, it's more likely to trigger a fault at high speed, but probably not on something that old, unless the split is bad enough the ring opens up enough for it to spin on the shaft/joint.

Quickest way to check, is to visually inspect each ring.

 

[Ubique]

ABS will work down to a stop, but the vehicle speed (generally) needs to be above 12mph before it will intervene, ABS doesn't only kick in under braking, it will intervene if it detects (or the wheel speed sensors) indicate slip of one or more wheels. If there is a broken, loose or damaged reluctor ring, I'd expect a DTC set for signal implausibility, given that it occurs at ow speeds in car parks (with lots of steering and wheel speed differentials), then it's more likely linked to free play in wheel bearings or steering angle sensor IMO.

 

[m_c]

Pure ABS only works under braking.
If it works under slip without the brake pedal being pressed, then it's also got TC.
And if it has a steering angle sensor, then it's a more likely to have ESP.

The issue is that age of ABS is not likely to have that great a diagnostic capability.
2002 would be in the era where manufacturers were transitioning from ye olde large inductive sensors, to more compact digital sensors.

I've spent far more time that I'd care to have done diagnosing this fault on various vehicles of that age.
If the ABS light was on, or the driver had said it had been, I would read the DTCs, but often a split ring won't store a fault.

 

[Neilj]

If the sensors are inductive then the generated voltage is very low at low speeds. A sensor to reluctor ring gap a bit bigger than it should be could be enough for the ECU to not register a speed signal and therefore it thinks the wheel is locked or not turning as fast as the others.
Visual checks and checking the four sensor values with some plug-in diagnostic reader would be my first checks.

 

[Ross365]

Nothing is showing in terms of dashboard warning lights.

I have a u840 memo scanner; I guess I could try that.

 

[Ubique]

Also jack up each wheel & check for free play in the wheel bearings.
I'm not really 'up' on Toyotas, I do remember there being some diagnostic bridging connector that with some combination of connecting pins together, reciting runes and rolling up of one sleeve, you can get the dash to output some flash codes - I think there's an extended data set too. TC came in on Bosch systems in '92/3 so it's possible that Toyotas could have it in 2002 vehicles.

 

[Memmeddu]

Hill holder?

 

[Guineafowl]

Had the same on a knackered Disco 3 belonging to a mate.

The steering angle sensor had failed, so the TC would kick in if you did a slow turn. Solution: turn off the TC and trade it in.

 

[charlysays]

I own a 2002 (Gen7) Celica, which is low mileage and generally in good condition. Just recently, I’ve started hearing what I’m sure is “ABS noise”, which just kicks in for a few seconds when I’m moving at very low speed (e.g. in car parks). It feeds back through the brake pedal too.

It’s been suggested to me that it could be a reluctor ring that sits underneath the sensor that has broken (apparently they rust and snap). Initial enquires suggest these cannot be obtained separately so it will be a new CV joint at ~£50. I’ve not had time to take a close look at it yet and I’m using my other car at the moment.
Can anyone offer any advice on this?

Thanks.

My Merc has done this too.
No fault codes either.
Basically the reluctor ring grooves had filled up with rust which is magnetic, so the pulse was weak. At low speed braking I could feel the abs coming on through the pedal. I chiseled out all the grooves in the reluctor ring, cleaned the sensor and problem solved.

 

[Ross365]

I chiseled out all the grooves in the reluctor ring, cleaned the sensor and problem solved.

I wonder if my Li-ion mini-drill with a small router tool might be good for that? Or even some citric acid in advance to soften it up?