Today, more and more passenger cars are utilizing an active suspension system, or a "smart" suspension. A smart suspension is similar to a traditional, or passive, suspension system since many of the same components are found in each. Shock absorbers or struts, bushings and suspension components all work together to provide good handling and a comfortable ride in both systems.
However, in a smart suspension system coil springs are replaced by air bags, which support the weight of the vehicle. These air bags, and usually the shocks or struts, are electronically controlled to respond to changing load and driving conditions. Most often the driver can also select a firmer or softer ride control setting to adapt to driving conditions.
In many systems, the suspension is air operated and controlled by a computer. This computer provides automatic front and rear load levelling by means of air springs. An air compressor supplies the air to the system and airflow is controlled by the interaction of the compressor, solenoids, height sensors, and the control module or computer. In addition to air springs, many systems also use dual-stage struts capable of changing their internal valving by means of a stepper motor.
The manufacturer for each individual model recommends specific maintenance and servicing procedures. Typically, diagnosis of these systems involves interpreting trouble codes from the vehicle's computer and electronically measuring the many motors and sensors in the system. Refer to the manufacturer's service manual for specific procedures.