Circuit Description

Control module uses no external circuits for operation that sets this DTC. Calculations that determine if this DTC is set are all internal to control module. Control module calculates a checksum on those areas of memory that hold critical operation data. This is done at a regular interval and is called periodic checksum. Control module also calculates a checksum on these memory locations whenever new data is written to them. This is called running checksum.

Control module compares periodic checksum to running checksum. If they do not match, control module sets DTC B1004 and control module reverts to base programmed critical operating data until new data is learned and stored in Keep Alive Memory (KAM).

DTC B1004 will clear from memory when control module makes a successful comparison of periodic checksum to running checksum. DTC will also clear when scan tool is used to clear DTCs.