saggy rear
 

2003 air inflater works, compresser does'nt come on to raise rear-end, replaced relay under mastercylinder. checked all fuses inside and under hood. idea's?

Welcome to HF.

2003 what? Year, Model and Miles should be included in every question. This section, like it says at the top is not for Tech Questions, strictly intro. Once you share what your question is about I can move it to the vehicle section where tech questions go.

sorry. 1'st time. it's a hummer h2.

As the tire inflator, this suggests the majority of the AS system is working e.g. ECU, Compressor, Airbag inlet valves.so not a relay or fuse.

Usually you'd get a "Service Air Suspension" message, however it seems some DTCs seem to be set without the message, particularly for the 2003

Might be worth getting it checked with a GM Tech2 scan tool, my guess would be a defective ride height sensor, hence the ECU doesn't attempt to inflate.

Have you tried operating the extended ride-height switch with the doors closed and engine running?

[Awaiting Resolution]

yes. you are confirming my last guess. to the shop for a code read. thank you.

ride-height wont work. agree with what you're saying. thank you.

hummerwalter any luck?