2004 XJ8 Vanden Plas air suspension fault warning is coming on. What does this mean. I have noticied the car doesn't adjust the height anymore. How do I check for problems? I checked above the front struts for leaks and dont see any. How do I know the compressor is even working? Something is definitely wrong as the back right and left of the car are at different heights. Any help would be appreciated

 

I have the same issue with my X358 XJR. The likely issues will be: Height sensors, failing pump or bladders. The pump you can buy a seal kit from ebay at $35 and it's an easy install. The sensors are approx $120 each and an hour labour and the bladders (unlikely as you've checked them) would be available at $450 each refurbished.

 

Did you see the ECAT "sticky" that's posted in this forum?

Air Suspension & ECATS System Summary: Components & Operation

Lots of good info in there.