DTC B1656: EEPROM Write Error & DTC B1658: EEPROM Checksum Error: Description
WARNING: This page is about a different car, the 1998 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Memory Mirror Module (MMM) performs self-tests on its EEPROM. DTC B1656 and B1658 will set if MMM detects a problem with the EEPROM. When DTC B1656 is set, module will store value being written on another block of EEPROM. When DTC B1658 is set, module will use default values for blocks of EEPROM that are corrupt. DTCs will clear when self-test indicates that EEPROM is okay.