P0501 (VSS issue) and a possible ABS malfunction?

I have a 2011 Jeep Liberty with 2 wheel drive and a 3.7L engine. It was bought used and has a P0501 code and an ABS indicator light. I am electrically inclined and have tools. But, I don't have access to a schematic. I do have a code reader dongle and use Torque.

All of the threads I find about the P0501 involve a sensor on the differential. However, I don't find a sensor on the differential. Can someone shed light on where it is supposed to be?

How can I determine which wheel is causing the ABS issue. Torque is not exposing any codes or other ABS issues.

If I could find out what kind of voltages I should expect, I could narrow down more. I did pull one wheel off and see no voltages. All fuses for ABS are active (has 12V). One of the fuses is only active when entered into Drive (at least it is active). But I see nothing at the wheel.

I could also test the sensor externally, with known voltages to test with (I don't want to apply 12V if it runs on 5V). It is a 2 wire sensor. I assume it is voltage in and pulse out).

Money and time is tight right now and I'd like to be sure what parts to get the first time. Any help is appreciated.