What's the mercedes suspension code 5501?

On Mercedes-Benz vehicles equipped with an air suspension, diagnostic trouble code (DTC) 5501 indicates a critical vehicle level problem in the rear. You'll need to have the code read by a STAR machine, and not a general scan tool -- it will be able to tell You more about the specific cause, and potentially track down a specific diagnosis. However, You're generally going to be looking at a failed air suspension compressor, a bad air strut, leaking lines, or a faulty relay. It's also possible that You have a faulty level sensor. You'll need more information so You can begin Your diagnosis in an informed way. You can, however, visually inspect the mentioned components, and hope that You get lucky.