Code 55 - ECM Error
WARNING: This page is about a different car, the 1993 Pontiac Grand Prix, 1993 Pontiac Firebird, 1993 Oldsmobile Cutlass Supreme, 1993 Chevrolet Lumina, and 1993 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
Ensure correct MEM-CAL or PROM is being used and that it is properly installed. If so, replace control module. Clear codes, confirm closed loop operation and check operation of SERVICE ENGINE SOON light.