A method of operating a memory controller, a memory controller, a memory device and a memory system are provided. The method includes reading first data from a nonvolatile memory device using a first read voltage, the first data includes a uncorrectable error bit, reading second data from a nonvolatile memory device using a second read voltage different from the first read voltage, the second data includes an correctable error bit, and reprogramming the nonvolatile memory device according to the comparison result of the first read voltage and the second read voltage.