speedkar9

Inside an ABS Motor

If you've ever wondered what an ABS motor looks like inside, I took one apart to see for myself.

Here's a video on whats inside:


The ABS system in your car uses wheel speed sensors to detect wheel rotation. A difference in wheel speeds indicates to the computer that the wheel is skidding. A a signal is then sent to the ABS motor, activating a solenoid temporary releasing brake pressure repeatedly within a short period of time, preventing wheel lockup.

To remove an ABS motor from your car, you need a 12mm wrench for the master cylinder brake lines, and a 10mm wrench for the 4 other brake lines going to the wheels. There's also a 10mm bolt and two wiring harnesses that need to be removed.



Here's what the motor looks like out of the car. (This one is off a V6 Solara with traction control from the junkyard, same unit as the ES300).



Prying off the plastic cover reveals some basic electromechanical circuitry going to 12 solenoids.



Taking off the solenoids involved me breaking the connection to the motor in the center. Here's what it looks like when the solenoids are separated from the valves:



On the other side there's a DC motor that is responsible for building brake pressure:



Wheel speed sensors are basically a magnet with a coil. As the splines of a CV shaft pass over the coil, it generates a change in voltage. You test it out by measuring voltage with a multimeter and passing a metallic object - even a screw - in front of the sensor and watch the voltage fluctuate.



ABS Sensor Replacement

As for the ABS sensors, they consist of a coil wrapped in a magnet. Here's how to replace one:


The problem I was having with my sensor was that the ABS was always kicking in on the front right wheel when I came to a stop.

First step is to jack up the car and remove the wheel.



Then follow the wire down the steering knuckle



The sensor is attached to the knuckle via a 10mm bolt:



I managed to snap my bolt



Remove the bolts and clip attaching the ABS wire to the strut and inner fender



Remove a few 10mm bolts on the splash guard and pull it back:



Then disconnect the sensor from the connection inside the fender liner and remove it from the car:



You can test the ABS sensor by measuring resistance. This is how the ABS sensor verifies each sensor is present and operational at startup. If the resistances are out, it throws an ABS code.

In my case I did not have an ABS code. My sensor measured 1700 ohms, the manual specifies 1600ohms.



I zip tied my sensor on for now. So far, no more ABS kicking in when coming to a stop. I sourced my ABS sensor from a junkyard car.

Fritz330

Awesome. Thanks.

speedkar9

I've updated the original post with a DIY video and pictures on how to replace the ABS sensor.

Oro

Actually I have. Thanks for that.

I'm confused a bit - are you saying your replacement sensor is 1700 Ohms? Because I can't see a functional difference in a 1600 vs. 1700 Ohm resistance in this application, both will give a return on/off signal within the tolerance of the ABS circuit.

I had this problem with an Acura last year; what I did to fix it was flush the fluid fully, then I used a wire wheel on the steel pick-up tip (adhered road crud and oxidation - looks like you've got a lot more of that in your neck of Canada than I do here around Seattle), and on the toothed ring wheel it senses.

speedkar9

I would have thought so too but it seemed like the replacement sensor which was within spec solved the issue of the wheel anti-locking as I come to a stop. Perhaps the sensor internally wasn't picking up the signals from the CV shaft or the ABS circuit is really sensitive. It wasn't enough to throw an ABS light though.

Robb92914

Thank you so much for this!! Doing this tomorrow!

speedkar9

All the best in replacing your ABS motor. You will have a series of brake bleeding to do to get all the air out though!