Hyundai Repair: Tone Wheel, hyundai elantra, tone wheel

Question
In a couple of your answers regarding a 2001 Hyundai Elantra with error code P0501, you mention a possible broken tone wheel.  What is a tone wheel and where is it located?  Is this something easy to replace/repair?

Answer
The tone wheel is a ring on the outer cv joint with square teeth on it.  To replace the tone wheel, you'll need to replace the outer cv joint or the entire axle.  

Whether this is an easy repair for you will depend on the tools you have available and how familiar you are with working on cars.  You'll need to remove the right front tire and separate the steering knuckle from the strut and the outer tie rod end in order to get the axle shaft out of the wheel hub.

You should verify there's something wrong with the tone wheel prior to replacement.  The problem could be with the right front wheel speed sensor itself or with the wiring.  I've seen a couple cars where rodents chewed through the wiring inside the fender liner.