How to cheque rear suspension on 2006 GMC Envoy

Air compressor for rear airsprings fail causing rear suspension to sit very low

Asked by for the 2006 GMC Envoy
bad air vale in compressor orbad seal
can you haer the compressor running, if you u have a leak at air bags or air bags themselves. seek a diag these can be a pain to repair even for a good mech.