Code 51: Mem-Cal Error
WARNING: This page is about a different car, the 1990 Pontiac Firebird and 1990 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
Ensure all pins are fully inserted in the ECM socket. If okay, replace PROM/MEM-CAL. If Code 51 reappears, replace ECM.