The inside ECM stores various specific data to correct the system even when there is no electrical power such as the battery negative terminal or No. 9 IGP (20 A) fuse are disconnected. But stored data based on failure parts should be cleared by using the ‘‘CLEAR COMMAND'' of the HDS, if parts are replaced.

HDS has three kings of clear command to meet the purpose. They are DTC clear, ECM reset. DTC clear command erases all stored DTC codes and Freeze Data. This must be done with the HDS after reproducing DTC during troubleshooting. ECM reset command erases all stored DTC codes, Freeze Data and all specific data to correct the system.