The data link connector (DLC) provides operating power for the scan tool at circuit 2140 -- battery positive voltage, and at circuit 550 -- ground). The DLC provides the Class 2 serial data signal at circuit 1807 and signal ground at circuit 451. The DLC provides the keyword signal at circuit 1319 -- for ECM and TCM, and circuit 1276 -- or the EBTCM. The scan tool will power up with the ignition OFF.