Suspension Air Bag Height Controls
Airbag systems control the vehicle's height by forcing compressed air into the pneumatic airbags to raise the vehicle and venting the air through an exhaust valve to lower the vehicle. A small compressor creates the air pressure that inflates the airbag to raise the vehicle, and a small electric solenoid vents this air pressure to lower the vehicle.
Airbag suspensions contain a height sensor that signals the ECM of the vehicle's actual curb/ride height. Modern systems lower the vehicle as speed increases. The ECM monitors the shared speed sensor signal over the bus and lowers and raises the vehicle as speed changes.
If the system is not working and not raising the vehicle scan for codes and visually inspect the system. These systems typically have a compressor to fill the air springs and a vent valve to exhaust them. If the compressor is not working, check the fuse and the circuit's connector for power and ground. If there's a problem with a vent solenoid vent valve, the vehicle will not lower once raised.