ECU Malfunction
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The BCM performs an electrically erasable programmable read-only memory (EEPROM) checksum as a part of its internal diagnostics as the BCM is operating. When the EEPROM checksum does not equal a predetermined value, DTC B1000 - ECU Malfunction sets. The checksum is the contents of each memory location in EEPROM added together.