Self Level Suspension Inactive

[we350z]

Posted on Facebook but thought I would try here as well.

My rear air bag suspension is no longer lifting on either side of my 2000 BMW X5 4.4i SAV. There is no sound coming from the compressor. I replaced the air springs last year with new Arnott bags. Car has been sitting for 6 months. I know I need to replace the height sensor on the driver side based on what the local indy shop told me from their inspection. I have been getting the "Self Level Susp Inact" dash message all along but in the past the compressor always kicked on and inflated both bags. I still need to check the fuses.

Questions:

1) Is there an easy to bench test the Wabco compressor to make sure it is functioning?
2) Will DIS give me any additional information?
3) Can I use a multimeter to test the height sensors? I have one new replacement sensor.

Thanks guys!