The parking brake system fulfills a vehicle’s parking function. The EPB system uses a motor that requires a self-diagnostic function for reliability. Reliability of the EPB is ensured by monitoring the status of the electric module and motor. This paper describes an EPB that consists of hardware to perform self-diagnostics after defining the DTC. The reliability of software is improved by autocode generating source code using variable tools. As the size of DTC increases, it accordingly becomes more complex. The EPB therefore uses a multiplexer because it requires many A/D ports. The EPB defines 23 DTC. The selfdiagnostic function performs well and detects errors when the EPB checks the performance depending on the test conditions.