Like many upper end radios (Mercedes, Lexus, Mazda 929, so on... These radios usually aren't prone to thinking they are being stolen, just because of a battery removal, unless the battery built in to the circuit board (Maintains Stations, clock and so on during very short disconnects has failed (Likely since 22 years from date of manufacture). OR during the time it was disconnected it was struck or jarred hard enough to make it think it was being removed without the security key (Usually a strange shaped piece of wire that inserts into special holes for proper removal. Or if something blew the fuse on the circuit board that acts as a backup safety for the dashboard fuses. After that, think about simply upgrading the radio to a newer one, most shops can put a really nice one in for under $400.00, about the cost of taking the old one in for testing and repairs.
