Code 51 - Faulty Prom/Mem-Cal
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1993 Pontiac Bonneville, 1993 Oldsmobile Ninety-Eight, 1993 Oldsmobile Eighty-Eight, 1993 Buick Riviera, and 1993 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
Ensure all pins are fully inserted in socket. If pins are okay, replace PROM/MEM-CAL, clear memory and recheck. If Code 51 reappears, replace control module.