Can I replace a faulty Logix5561 CPU with Logix5555?

Please, I need help, can I replace a faulty Logix5561 CPU with Logix5555,doing I/O configuration, please I need advice

You would need go convert your program using the different Processor module and firmware. You would need to verify that the replacement processor is supported by the version of Logix you are using. If it does then you should be able to use the L55 processor in place of L61, assuming that the L55 memory capacity is sufficient for your application