A fault detection system (10) and computer-implemented method for detecting a fault in a cab signal system (100), including: a plurality of sensors (12) in electrical communication with a cab signal display circuit (106), each associated with a respective one of a plurality of lamp circuits (108) and configured to sense or measure: presence or absence of voltage, voltage level, voltage drop, presence or absence of current and/or current level. A monitoring unit (14) is in communication with the plurality of sensors (12) and generates circuit data (16) representative of at least one condition of at least a portion of the cab signal system (100). A computer-implemented method for detecting a cab signal aspect of a train (T) is also disclosed.