Code 55, ECM/Pcm Error
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1995 GMC Vandura, 1995 GMC Rally, 1995 GMC Pickup, 1995 Chevrolet Sportvan, and 1995 Chevrolet Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Ensure control module grounds are good and MEM-CAL is properly latched. If okay, replace control module. Clear codes and confirm closed loop operation. Check operation of SERVICE ENGINE SOON light.