Air suspension inop.

Your air shocks are not working
you should have an air pump in the back end of your car which pumps the shocks up but the pump may be worn out as well the air lines may have holes in them. If the pump is working you will hear a humming as the pump works.
My pump was shot and my shocks were worn out so I replaced them with manual air shocks you pump up with an air compressor with the hose coming out under my bumper out of sight. I check them every six months and top them up. Sure cheaper than buying the pump and all the trimmings.

leak in the bags or check valve bad or stuck.

If you have seen lower back several times but the car raised by itself before, then you have to replace air spring. I replaced those with Arnott air spring.
If you had this problem for the first time, your air spring will be fine. If you have 4 corners air spring and the front one blows air in and out, your pump is okay.
Then I will first replace air suspension relay which costs $30. And you will have to check air hose connection. Finally you could try to replace air pump.

I have a 2000 Lincoln Town car, had the same problem, it was the rear air suspension/shocks. They are air bags basically that levels your car and it cost about $300.00 for each at the dealer for parts and install but it also has its own motor that inflates and deflates these air bags and I also had to replace that and that cost over $400.00 installed at the dealer.

If a slow air leak has developed in either an air bag or in any of the tubing (there's a lot) or in the valve at the air pump, you will hear the air pump running more often.

Eventually, the pump will be unable to raise the car to the required height (working against the leak) within the time-out period (about a minute) and then it will give up, stop pumping, and a light on the dash will come on indicating an air suspension problem (or maybe on your relatively newer car, the digital dash may show an error message - I don't know).

I've had an '88, a '91, and a '94. Both the '91 and the '94 had air suspension faults at various times, and none of them were air bag leaks. I've had the valve at the pump stick and/or/leak on both cars, and the tubing spring a leak on one as well. Apparently the air bags are pretty well made and don't fail as often as the other components (in my experience).

Problems with the air suspension seem to be less frequent with the Sport than in previous Range Rover models, but they still do occur. One owner reports "Whenever my RRS is lowered to "access" level a suspension system fault message apprears.". Another reports " Had the RRS back less than 2 hours and another "suspension fault." Also kept receiving messages that the vehicle is raising slowly and vehicle will raise when system cools. Couldn't even drive because it wouldn't raise out of access mode. Anyway, back to the dealer. Picked the RRS up again today-dealer said the EAS compressor was faulty and replaced it. So far everything is ok." Overall, most of the problems seem to be related to bad suspension height sensors or bad compressors. Angus Wade of the Czech Republic had his suspension light come on when in Germany; it started yellow and then red, then disappeared when he stopped and restarted the engine -- and has not happened since. His dealer said they have seen this a bit.

Weak Compressor: An official Technical Service Bulletin (TSB) LS-204-004 addresses "ELECTRONIC AIR SUSPENSION (EAS) WARNING MESSAGE AND LAMP ILLUMINATION". This deals with the warning message "Suspension Fault - Normal Height Only" message appearing with the Air Suspension Warning Lamp on. Computer diagnosis shows pressure increasing too slowly or unable to pressurize, with no air leaks. The usual problem is the compressor exhaust valve sticking, causing an internal air leak when the compressor is active. The bulletin recommends renewing the air compressor (RQG500090 is the latest specification air compressor with a stronger exhaust valve return spring)and installing and updating the air suspension control module software using WDS disc 13 or later.

Suspension Fault Message (random): One owner reported getting random suspension fault messages on his brand new RR Sport purchased in June 2006, well after the fix was in for the weak compressor. His suspension Fault message and Suspension Warning Light (Amber) came on after 5 days of ownership. He stopped and restarted the car, which caused the light and message to disappear, but they came on again after 5 minutes. Later the same day, the warnings disappeared again.

I have heard that on 2006 models, EAS fault messages can be caused by an internal leak in the Air Suspension compressor exhaust valve. The fix is said to be replacing the compressor updating the software.

Hope helps.

Problems with the air suspension seem to be less frequent with the Sport than in previous Range Rover models, but they still do occur. One owner reports "Whenever my RRS is lowered to "access" level a suspension system fault message apprears.". Another reports " Had the RRS back less than 2 hours and another "suspension fault." Also kept receiving messages that the vehicle is raising slowly and vehicle will raise when system cools. Couldn't even drive because it wouldn't raise out of access mode. Anyway, back to the dealer. Picked the RRS up again today-dealer said the EAS compressor was faulty and replaced it. So far everything is ok." Overall, most of the problems seem to be related to bad suspension height sensors or bad compressors. Angus Wade of the Czech Republic had his suspension light come on when in Germany; it started yellow and then red, then disappeared when he stopped and restarted the engine -- and has not happened since. His dealer said they have seen this a bit.

Weak Compressor: An official Technical Service Bulletin (TSB) LS-204-004 addresses "ELECTRONIC AIR SUSPENSION (EAS) WARNING MESSAGE AND LAMP ILLUMINATION". This deals with the warning message "Suspension Fault - Normal Height Only" message appearing with the Air Suspension Warning Lamp on. Computer diagnosis shows pressure increasing too slowly or unable to pressurize, with no air leaks. The usual problem is the compressor exhaust valve sticking, causing an internal air leak when the compressor is active. The bulletin recommends renewing the air compressor (RQG500090 is the latest specification air compressor with a stronger exhaust valve return spring)and installing and updating the air suspension control module software using WDS disc 13 or later.

Suspension Fault Message (random): One owner reported getting random suspension fault messages on his brand new RR Sport purchased in June 2006, well after the fix was in for the weak compressor. His suspension Fault message and Suspension Warning Light (Amber) came on after 5 days of ownership. He stopped and restarted the car, which caused the light and message to disappear, but they came on again after 5 minutes. Later the same day, the warnings disappeared again.

I have heard that on 2006 models, EAS fault messages can be caused by an internal leak in the Air Suspension compressor exhaust valve. The fix is said to be replacing the compressor updating the software.

Hope helps.

FIRST YOU TURN OFF AIR SUSPENSION SYSTEM.YOU LOCATE THE AIR SUSPENSION SWITCH WHICH IS ON THE RIGHT KICK PANEL.WHEN YOU TURN OFF AIR SUSPENSION SYSTEM.YOU LOOSEN REAR LUG NUTS THEN SAFELY RAISE AND SUPPORT VECHICLE. REMOVE TIRE.REMOVE ELECTRICAL CONNECTOR FROM THE AIR SPRING SOLENOID.THEN SLOWLY DISCONNECT AIR LINE FROM SOLENOID SLOWLY BLEED AIR FROM SOLENOID.

I have owned several air suspension vehicles. My Expedition was similar to yours. You may want to try the 4x4 switch because it will raise the body 1-2 inches higher. Checking its fuse would not hurt.

On most of my vehicles the suspension would work end to end, raising the front first. You could have 2 issues with the suspension. There should be valving to switch the air to the rear suspension after the front is up. I would wait longer for the rear to catch up.

If I had to guess why the front lifts first it would be to get the front off of the curbs and sidewalks when you park so the bottom doesn't drag.

There is a diagnostic plug for the air suspension and sometimes Autozone or Oreillys have the scanner for that special plug. If not, some alignment shops and all dealers would have it. Also Ford parts are often the same as Lincoln and cheaper., Someone may make aftermarket parts at a better price.

The suspension compressor is located below the air cleaner assembly.It also opened the fuse in the underhood fuse panel 30 amp. The cost depends on where you have repaired, the dealer will be more, but you get a better warranty on parts and labor.