DTC B1658: EEPROM Checksum Error: Description
WARNING: This page is about a different car, the 2001 Cadillac Seville. However, it is still accessible from the selected car via links, so may be relevant.
EEPROM check sum error detection is handled inside control module. No external circuits are involved. Control module retains an inverse copy of digital value stored in certain blocks of memory in EEPROM. Control module then reads information from certain blocks and adds stored inverse value to current value. If they do not equal zero, control module will store DTC B1658. When DTC is stored, control module reverts to base operation values programmed for those blocks of data. Blocks of data that did not fail check sum test are not affected.