I had the same thing when I first bought my 4.8. It was a leaking airbag. This threw out my EHC so don't let it go too long leaking. If you have INPA you can also change your ride height with it. You will need two people but you can just unfollow and fill the airbags as necessary and then set ride height where you want it when you're done. When I first replaced my airbags, my EHC was bad so I couldn't use DIS to set ride height. Used INPA to do and initial "lower" ride height and once I fixed the EHC I used DIS just to make sure I knew how to use it.