I've had the dreaded ABS light for several months and finally decided to tackle it. I had the code read at a shop and they told me there was no signal coming from the left front speed sensor.

I checked the resistance and it showed identical to the sensor on the other side. I clicked over to AC on the meter and spun up the tire. I got a voltage increase, showing the sensor works.

This leads me to believe that there is a wiring problem above the sensor somewhere. The sensor plugs into a socket that disappears into a larger wiring loom and I don't know where to look from there. My old Haynes manual ABS section is useless to me. How can I go about tracking down the missing signal?

2000 F150 XLT 4WD 5.4L.