A replaceable unit includes a communication unit to perform communication with a main body, and a non-volatile memory storing code information indicating whether a configuration of an error detection code is a first configuration or a second configuration. The communication unit stores, in a volatile memory, the code information, executes the communication in accordance with the code information in the volatile memory, and, upon receiving a change command, updates the code information stored in the volatile memory. The first configuration uses an error detection code of a first code length, the second configuration uses an error detection code of a second code length longer than the first code length, and the first configuration is used for the change command in order to change from the first configuration to the second configuration.