Chart B4 Main Relay Circuits: Notes
WARNING: This page is about a different car, the 1990 Buick Riviera and 1990 Buick Reatta. However, it is still accessible from the selected car via links, so may be relevant.
Main relay supplies 12 volts to EBCM, through pins No. 3 and 20, to operate main valve, solenoid valves, logic circuit and self-checks.