WARNING: This page is about a different car, the 1990 Cadillac Fleetwood and 1990 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Test Number 1)
With engine at idle, EGR solenoid should be energized. Test light across EGR solenoid terminals should be lit.
Test Number 2)
Check ECM's ability to turn solenoid off.