US Patent 9434308 System for detecting the integrity of a lighting circuit

A status monitoring circuit for monitoring the status of an external device coupled to an electrical system of a vehicle, the status monitoring device including a sensing unit coupled to the external device and configured to sense an input voltage and an input current at the external device, a monitoring unit coupled to the sensing unit and configured to determine a normal operation of the external device based on the sensed input voltage, and, in response, to detect an undercurrent condition of the external device based on the sensed input current, and a status indicator coupled to the monitoring unit and configured to display a fault indication in response to the monitoring unit detecting the undercurrent condition.