The air bags from my envoy keep going down when parked on a hill or someone heavy in on it. Can i control it to be leveled?

that will usually mean that the air bag has a small leak, or the line going into the bag could be linked or possible pin hole in it , also it is a good idea to have the entire system checked as some of these systems have a leveler rod or mechanism which can be per wheel or per axle. which is what keeps these vehcles level.

well I will tell you my problem it maybe the same happening to you, every time I park the car for more than 4 hours it will lower the rear and after I start it will go to normal high, well the car have a air leak on one of the air bags in the rear, the compressor was pumping air almost all the time because of that to the point that one time just stop working. I have to buy new air compressor and 2 air bags. I bought them at www.arnottindustries.com not difficult to replace either.

It may be that your leveling sensor is going bad. The sensor thinks the bag is low on air, even with the key off.

The air system does not lower when you get out, it levels the car and stays level, but is you put weight in trunk and people sitting in the back seat and the car lifts to level out with the weight and then you remove all the weight and rear end is to high up then there is a problem.
These bags do not lift that high, if you hear the solenoids make sure it is not lower , measure.Also, the release of the air is very slow, make sure it is not lower, if you hear the solenoids open the car may be lowering very slow. check the height.If you are sure its not lowering then you may be correct in saying the level sensor may be bad. the only other part would be the solenoids but i would start with the level sensor as the air is going into the bags.
I quick test to check solenoids at bags is to start car and go rear the rear and locate the sensor, remove the arm from the control arm and bring it down so computer thinks car is to high and see if air is released. caution don"t stay under the car as it will lower down slowly. if it starts to lower then turn key off and reconnect lever and replace sensor.there is a company we use that is real good at this air bag system and prices are good with quality parts.http://www.arnottindustries.com/part_LINCOLN_Air_Suspension_Parts_yid2.html

The air suspension system should stay up for several days without going completely down, which probably means that you have a small leak which is quite common even on relatively new air bags or struts.

A general rule of thumb is that if the compressor isn't kicking on several times during a drive then they are good to go. The air bags are a pain to change, so most people don't change them until they are really bad.

well depending on witch way you are on the hill if the back is going downwards have someone push on the back of it while you try to put in gear. make sure to always put the parking brake on before you put it in park when on a hill this keeps it from putting all the weight on the trans.

My experience is that cruise control works on level roads, uphill you have to control speed yourself same for downhill. Exception is very powerful cars. Did it maintain speeds before? (uphill + downhill)

Spray the air bag connections to the air lines and the compressor connections with a 10% dishwashing liquid / water solution in a spray bottle while the engine is running, in park, on a level surface. You'll easily see the bubbles when the solution contacts the leaking area.

Spray a soap and water mix on the bags in the rear while they are aired up and watch for bubble's to locate the leak.

sounds like the level position sensor