Code 51, Faulty Prom/Mem-Cal
WARNING: This page is about a different car, the 1992 Pontiac Grand Prix, 1992 Oldsmobile Cutlass Supreme, and 1992 Chevrolet Lumina. 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.