A system and method for testing operation of that portion of a transportation vehicle's electrical system that has switches accessible for selective actuation by an occupant of an interior of the vehicle to control exterior lamps through an ESC (12). During a learn mode (56) of a test, processor apparatus executes a learn algorithm stored in the ESC and as the learn algorithm executes, a person inside the vehicle operates the switches in a desired sequence to cause the ESC to store data related to the sequence. During a playback mode (58) of the test, the processor apparatus executes a playback algorithm stored in the ESC to cause the ESC to actuate the lamps in accordance with the stored data. A defect in any portion of a lamp circuit is observed by failure of a lamp to illuminate in the stored sequence.