A while back the 2000 STS with F45 started showing a "service suspension system" display on the DIC intermittently, now it's on all the time and the rear end of the car is riding very low. I don't hear the ELC compressor running at all. Checked for current codes, this is what I have:
Driver Door Module
DDM B1982 Device Power Circuit High
Road Suspension System
RSS C0690 Damper Control Relay Circuit Malfunction
RSS C0896 Electronic Suspension Control (ESC) voltage is outside the
normal range of 9 to 15.5 volts

I located and swapped the damper relay with a known good relay, no change. I checked all the fuses under the back seat and they're good.
I'm having no luck finding more specific diagnosis info or wiring diagrams. I really don't want to drop the exhaust system until I know what to look for.
Guess I'm going to have to break down and get a GM shop manual.

Any constructive advice welcome,
k