DTC B1009: EEPROM Checksum Error: Description
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. 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 compares its previously stored checksum with checksum calculated when ignition switch is first turned to RUN position. When DTC B1009 is stored, control module will operate from preset critical operating data for those blocks of data that have failed check sum test. Blocks of data that have not failed check sum test are not affected. DTC will clear when control module runs a successful check sum test of EEPROM.