Another self level inactive question

[dlsderoo]

I have a 04 4.8is with this famous sel level inactive on the dash. I have checked the 30 amp fuse and it was fine and I replaced it anyway also I replaced the relay.
So my truck is level no air leaks but the compressor has not come on in 2 weeks and it is starting to look like its getting lower in the back after 2 weeks. Can I actuate the relay to fill the airbags up to buy more time to troubleshoot. What is the best way to tested the level sensors. I dont have any water or any signs of moisture in the battery compartment and everything looks brand new like the compressor and control module.
Thanks
Craig