Cruise Control Unit Ground Circuit
WARNING: This page is about a different car, the 1992 Subaru SVX, 1992 Subaru Legacy, 1991 Subaru Legacy, and 1990 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.
Turn ignition off. Measure resistance between ground and terminal No. 10 of cruise control unit connector. If resistance is more than one ohm, repair ground circuit.