Code I056 - IPC EEPROM Error
WARNING: This page is about a different car, the 1995 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
This code sets when IPC cannot "read" elapsed odometer mileage in EEPROM. ERROR will be displayed in odometer display when code is set. Check IPC harness connections and EEPROM insertion into IPC. If connections are good and secure, replace IPC.