GM Service Manual Online
For 1990-2009 cars only

The exhaust solenoid is located inside the automatic level control air compressor head and provides two functions:

    â€¢ When the automatic level control sensor energizes the exhaust solenoid, the solenoid provides a path for the exhaust air to leave the system.
    â€¢ The exhaust solenoid acts as a blow-off valve in order to limit maximum system pressure to approximately 1240 kPa (180 psi).