my 2004 gmc envoy is sagging in back
Its possible your air compressor has failed, the switch could be faulty or the air bag has a leak...
I just see coil springs in the back, Probably have a broke coil spring. If this is the case, both of them should be replaced.
Looking for a Used Envoy in your area?
CarGurus has 31 nationwide Envoy listings starting at $3,990.
Search GMC Envoy Questions
GMC Envoy Experts