There is a switch on the OBDII block that plugs into the vehicle's diagnostic port labeled KEY and BATT. Make sure that the switch is set to the KEY position. If the device still does not turn off and is equipped with the accessory power wire, check the fuse that the power wire is connected to and make sure that fuse does not have power when the key is off. The power wire needs to be connected to a fuse that only has power with the key on.
