A surgical instrument system can include an end effector and a staple cartridge which is removably insertable into the end effector. The staple cartridge includes a sled movable from an unfired position to a fired position to eject staples removably stored in the staple cartridge. In various instances, the sled can be inadvertently advanced from its unfired position when the staple cartridge is positioned in the end effector, for example. The surgical instrument system further comprises one or more sensors configured to detect whether the sled is in its unfired position and/or whether the staple cartridge has been mis-inserted into the end effector. The one or more sensors can also determine whether the staple cartridge has been fully seated in the cartridge channel.
