A control module reflash system includes a control module located in a vehicle that controls at least one function of the vehicle according to stored vehicle software. An external interface module receives a software file from a source external to the vehicle and receives a part number for the stored vehicle software in the control module. The external interface module retrieves a comparison software file from the source external to the vehicle corresponding to the part number and compares the software file and the comparison software file. The external interface module identifies differences between the software file and the comparison software file, generates a compressed file based on the differences, and provides the compressed file to the control module. The control module generates a flash file based on the received compressed file and the stored vehicle software and modifies the stored vehicle software based on the flash file.