2002 Navi suspension sunk in rear

OK, I was selling my '02 Navi, I let a guy test drive it...by himself. He returned 20 mins later. I get in it the next day and I noticed it riding weird. Ck Susp light comes on and the rear end won't go up.

Now, this could be totally coincidence, but now I have a problem, just weird.

I guess the fuse would be first step,,,anyone know which fuse???

Relay next step, passenger side under bumper???....How do I tell it's bad????

Any other ideas????

Front end still at normal height...
I don't hear the pump come on when it goes in gear either???

I drove it around the block and could hear the pump kick on and off, but rear didn't move.
?????????????

Just a few threads down, this was discussed is some detail.
The OP and last responder were finally able to diagnose and fix the problem:
http://www.automotiveforums.com/vbulletin/showthread.php?t=743019