DTC B1009: Checksum Error In Control Module: Description
WARNING: This page is about a different car, the 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, 2001 Chevrolet Monte Carlo, and 2001 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Internal fault detection is handled inside control module. No external circuits are involved. DTC B1009 is set when control module detects a check-sum error in internal memory. When DTC B1009 is set, microprocessor refuses all additional inputs. Current DTC B1009 will clear and become a history DTC when microprocessor makes a successful check-sum maneuver with Electronically Erasable Programmable Read Only Memory (EEPROM). History DTC B1009 will clear after 100 consecutive ignition cycles if problem for malfunction is no longer present.