ABS issue with Caddy STS...help?

My Caddy STS brain says it's not getting any input from the front wheel speed sensors. However I can get a wave signal on the 0 - 0.5 volt scale when I hook up to the sensor and spin the wheel. I've checked the wires and don't see any issues, but haven't done any continuity checks as it's darn near impossible to see where things go. I did pull the body control module and checked connections, cleaned things, and hooked it all back up. But the problem persists. Does the brain send voltage to the sensors and then the sensors convert this into waves and send the signal back to the brain? I'm not exactly sure how this works....any help would be greatly appreciated. Thank You.