Which of the following is the most likely cause of backup lights not functioning?

The most likely cause of backup lights not functioning is a faulty backup light switch. This switch is specifically designed to activate the backup lights when the vehicle is shifted into reverse. If this switch fails, it may not send the signal to turn on the backup lights, resulting in them not functioning as intended.

While corroded connectors, burned out light bulbs, and damaged wiring harnesses can also lead to lighting issues, a malfunctioning backup light switch is often the primary component responsible for initiating the light operation when the vehicle is in reverse. If the switch is not working properly, it will prevent the backup lights from receiving power, regardless of the condition of other components in the circuit. Therefore, identifying and addressing a faulty switch is crucial for restoring function to the backup lights.