Disconnect Battery
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.
NOTE:
On many OBD-II systems, ECM will retain memory for an extended period of time with battery disconnected. Memory may be retained for several days.
Disconnecting ECM power or battery ground will clear all ECM memory including DTCs, freeze frame, failure records, adaptive learning and system monitors.