Finally found some time to get under the car (at least the front, while I was doing control arm bushings!). Here's what I found:
-arm is good, but squeaks through range of motion
-plug is clean and corrosion free
-headlights appear to be doing power on self test again after unplugging/plugging in front level sensor
-lights did power on self test with front sensor plugged in and with front sensor unplugged
-lights adjusted approx every 15 seconds to manually moving sensor arm, but failed to repeat (possibly intermittent sensor failure??)
-noted that 3 of 6 pins (pins 1, 4, 2) are wired at connector, 79 ohms across 1 and 4, nothing across others, resistance remains 79 ohms at all arm positions
I'm thinking it's probably a bad front sensor. What output should I get on this sensor?