To provide a fault part detection system capable of facilitating and ensuring the specification of a fault part and simplifying the replacement work procedure thereof.

This detection system comprises a substrate 2 having a plurality of electronic part 1 mounted thereon and a control part 3, and the control part 3 has fault part detecting function and hot swap function. The electronic parts 1 are mounted on the substrate 2 through electric lock means 4A and 4B and pressing means 5. The substrate 2 is provided with a nonvolatile memory 6 having a substrate-side lock release code stored therein, and the control part 3 transmits this code to the electronic lock means 4A and 4B. Further, the electronic lock means 4A and 4B have the function of comparing the substrate- side lock release code with the lock means-side lock release code and releasing the lock when the matching of both the code is judged.