'91 stock vert

With ignition in on & start positions there is a loud, constant buzz and all the idiot lights stay on (air bag light eventually goes out).

Once the engine starts or the ignition is turned back to off or accessory position the buzzing stops and the idiot lights go out. It is annoying and I can't check my engine error codes!

Have searched forums, but have not found this specific problem discussed.

Thanks if you are with me so far!