Alright I have the same problem now but I wanted to get some input. Every single pixel on my dash is completely burned out so I'm not seeing the Self Leveling Suspension error message, but I walked out to my car and the left rear was dumped. However as soon as I start my car, it raises back up. (this has happened 3 times this week)
I'm HOPING it's also just the sensor like yours but has anyone experienced any problems with the actual airbag/strut being messed up or needing replacement?

I'm going to give the sensor a shot since it's cheap, but another question I have is, where is the pump located? Or what fills the shocks with air? Is it an air suspension? What controls the ride height/leveling? I just want to check and see if there are any leaks in the lines?

Oh also, someone mentioned a fuse. Where can I look for the fuse that control this?

Thanks guys.