Generic -- diag air suspension not going down/up

to check if air dump solenoid bad, remove air line that will be supplying air to air bags and turn on switch see if air comes out, if not replace solenoid

ANY MAKE/MODEL

IF AIR SUSPENSION NOT BUILDING:

if air suspension not building up:
- check air tank has air
- if air tank has air, check after air tank
- drain all water from water, if any

common areas on cummins:

air compressor intake hose,