ABS System?

[huesmann]

How does the ABS work on our cars? I know there's a sensor on each knuckle, but AFAIK there's no reluctor ring. How does the sensor determine wheel speed?

 

[negusm]

43-701B is the sensor and it watches the axle through the knuckle. So I'm going to logically say that the CV Axle assembly has lines on it or splines that work with that sensor.

 

[negusm]

After some digging, there are magnets embedded in the axle that when spun the sensor picks up on.

Those reluctor rings like you mentioned are for very early ABS designs. I remember that ring in my old '96 Probe GT.

Regardless, all(?) ABS sensors use magnets for sensing.

 

[huesmann]

So if there's an issue, I assume the sensor is more likely to be the problem than the axle.

 

[negusm]

Yeah, the axle is probably not an issue. It'll be the sensor, wiring or ABS control module.

 

[huesmann]

Could the module go bad on a pothole hit?

 

[negusm]

I don't know. Maybe? You'd have to diagnose it. I am really only familiar with the ABS module under the hood where the brake lines go in and out. We had that module go bad due to an internal valve sticking. This didn't produce a code or ABS light, just a very very soft pedal. If you have an ABS light, I don't know where that gets thrown. Maybe that unit or the ECU?

 

[huesmann]

I hit a pothole and the car eventually lit up the ABS, steering wheel, traction control, AT, airbag, and parking brake lights. That's what led me to believe there was an ABS/VSS issue.

 

[huesmann]

Well, turned out to be real simple after all. I had a piggyback fuse holder that I was using as a 12V source. It just popped out of the socket in the passenger side fuse panel. It just so happened that I selected the ABS fuse there to piggyback off of.