Air suspension is not working

check for an air leak in the suspension, hoses or valves
it sounds like the air compressor/pump is cycling to maintain air pressure

Would need to know what DTC'S - diagnostic trouble codes are stored in the module for the autoride suspension . Hooking up a professional type scan tool ,looking at input data to the module etc... Looking at a wiring diagram an testing electrical circuit's using a DMM - digital multi-meter . Reading how the system works ,what all involved in making the system work . This is how a professional Tech would go about diagnosing this .

The automatic level control (ALC) system maintains a desired rear suspension position under all types of towing, hauling and loading conditions. The following components are involved in the operation of the ALC system:
• Air line tubing--Pressurized air from the ALC compressor is pumped to each of the rear shocks via air line tubing.
• Air drier--Pressurized air from the compressor is run through a drier containing a moisture absorbing chemical preventing water accumulation in the rear shocks.
• Compressor--Supplies pressurized air to the rear shocks
• Compressor motor relay--The relay supplies battery positive voltage to the ALC compressor motor.
• Pressure sensor--The electronic suspension control module (ESCM) module provides a 5-volt reference and low reference to the ALC pressure sensor. The module receives the signal voltage that is relative to the air pressure applied to the rear shocks.
• ESCM--Controls the ALC system and electronic suspension control (ESC) system and detects failures in both. The module monitors inputs from the position sensors, and pressure sensor to determine when to raise and lower the vehicle to trim height as the vehicle is loaded or unloaded. The module limits pump activation to 255 seconds to prevent thermal damage.
• Exhaust valve--An electric solenoid activated by the ESCM to vent air pressure from the rear shocks.
• Left and right rear suspension position sensors--The module provides a 5-volt reference and low reference to all 4 of the body-to-wheel suspension position sensors. The sensors send the ESCM a signal voltage that is relative to the rear suspension ride height
• Left and right rear shock absorbers with internal air chambers and dampers--Dampens the rear suspension and maintains trim height depending on the air pressure applied.

Need a repair shop to diagnose the
air ride system
Can't guess form here,always need the
patient

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).

sounds like you have a bad pump. I have fixed dozens of them and 99 percent of the time it is a pump. the other thing is a pump relay or the control module. but not likely.

the air pump has gone out. possibly because of air leaking from air springs. non stop air pump working has wore it out and may need replacing.

Air suspension needs compressed air for the control of Air Springs (Air Spring is a cylinder like thing which goes up and down when air is pumped in and out of it). For pumping in and out the air, air compressor needs to be switched ON/OFF. Compressor relay connects and disconnects the compressor motor from the power supply ( battery). ----------------- air ride suspension compressor located under the air filter box . ---------------- the Air compressor clutch relay location
is fitted to the left hand inner wing (when viewed from the the driving seat).
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the compresser is located on the left hand side of the car under the hood.
once you open the hood remove the air cleaner housing and windshield washer resivor.
there is a panel that you lift up under both of thoese that is where the compresser is located
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1. The air suspension uses a small, separate air compressor under the driver's side left fenderwell, with air lines running to the air bags. On the top of each air bag is a electrical valve. This is a relief valve that allows air to be exhausted when activated, and which senses the amount of air pressure within the air bag to keep both sides equal. These valves are operated via a leveling sensor that is attached to the body of the car and to the rear axle by a movable arm. When the rear of the car drops due to increased load, the arm is pushed up. When the arm is pushed up, it turns on the air compressor and fills the air bags to level the car. When the load is removed and the arm moves down, indicating that the back of the car has risen, the sensor opens the valve on the air bags and allows air to escape, lowering the car.
2. If the back of the car is low, indicating that the air suspension is not working, and the air suspension light is on, check the fuse first. If the fuse is all right, check the air suspension switch in the trunk and make sure it is on. This switch is used when the car is in for service. Always turn off the switch before lifting the car, because the sensor will think the car is rising and keep the air bag valves open, ruining the rear air suspension.
3. Turn the ignition key with the engine off. Listen for the compressor to come on while pushing down on the rear bumper. If it does not come on, test the switch terminals for power, using a circuit tester. If one terminal has power and the other does not, replace the switch. If there is power, turn the switch to the off position, raise the vehicle and place it on jack stands in the rear. Inspect the leveling switch on the axle, making sure it is not bent and is connected. Use an ohmmeter for this test. Pull the electrical connector off the switch. Loosen the arm of the switch from the axle. Test the switch with the ohmmeter by checking across both terminals while slowly moving the arm. There should be no continuity with the arm down. As the arm is raised, there should be continuity. If not, replace the switch. If there was continuity, connect the arm and the electrical connector.
4. Put a floor jack under the axle and raise the axle to the point where it is just beginning to lift the car off the jack stand. Turn on the ignition. Turn the air suspension switch to the "on" position. Use the circuit tester to check for power at the leveling switch. If there is power, turn the air suspension switch to "off" and lower the car. Access the air compressor in the front, under the hood, and check the electrical connector for power. If there is power, check for a good ground. If both are good, replace the compressor. If the compressor works and the car does not rise in the back, replace the air bags.

Sounds like the problem is in the air bag suspension, not the compressor. The air bags shouldn't be losing air when the car sits. The compressor adjusts the suspension level according to the load. The air bags have a valve similar to a blow up raft that allows air to pass through both ways. If when the car is running the compressor is constantly running and not turning off, the issue is within the air bags and/or the air line.

Unplugging the Connector will cause the Check Suspension light to come on as its listed as a fault as it cant run.

But with it unplugged the compressor shouldnt been able to start. If you want to kill the compressor pull its relay from the engine bay. located above the battery.

But i'd suggest correcting the fault as if those bags do pop your going to end up being grounded. as the rear will drop a fair bit!

if it makes the noise when you first start and then goes away It is probably the air suspension pump coming on like normal. These pumps have a tendency to be noisy. if there is no noticable problem with the suspension except for the noise I wouldn't worry about unless the noise bothers you.It is about a $500 repair