Yet another air suspension ?
 

03 H2, got the dreaded Service Air Suspension warning. Changed out both air bags and still didn’t fully lift. Replaced the Relay and lifted better but still sagging. I know the compressor runs as I used it to fill things with the attachments. What else could it be? Both height sensors out at the same time? I’m ready to convert to coils like most everyone seems to have done, but would like to save the air system if I can.

You need a Tech2 so you can reset the system height. Supposed to use a couple of special blocks to hold it at just the right height. I used a jack (I have a Tech2) and actually had to jack mine to be slight off-level in the other direction when I set it with the Tech2 so that it would hold as level.