DTC B1009: EEPROM Checksum Error: Description
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2002 GMC Savana, 2002 Chevrolet Chevy Express, 2001 GMC Savana Special, 2001 GMC Savana Camper Special, and 2001 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
The EEPROM check sum error detection is handled inside the control module. No external circuits are involved. Microprocessor retains an inverse copy of the digital value stored in certain blocks of memory in EEPROM. Microprocessor then reads information from those certain blocks and adds stored inverse value to current value. If they do not equal 0, microprocessor sets DTC B1009. Microprocessor reverts to base operation values programed for those blocks of data that have failed checksum test. The blocks of data that have not failed the checksum test are not affected. A current DTC clears when malfunction no longer exists. A history DTC clears when module ignition cycle counter reaches the reset threshold, without a repeat of malfunction.