The height sensor mechanism is just inboard and forward of the rear left tire. Remove the left rear tire and look for a mechanism with an arm (height sensor arm) coming out to the rear, and a rod (sensor link)attached to the arm. Look at the components to see if anything looks damaged, disconnected or out of place.
Accessory inflator button, RIM and height sensor mechanism are the most likely culprits.
I have the height lever and switch it connects to, and the Rear integration module out of a 00 SSEi. If you think it will work for you, I'd let them go cheap. $25 shipped. They should work, but I have not tested them personally.
I believe they have a similar system. They did have the rear air assist, and if you have the trunk inflator, there is a good chance you have it. i would also check the mounts and springs if they are not level side to side.