If a customer complains that all brake lamps are out and cannot shift out of park, what is a likely cause?

The situation described indicates a problem with the brake lamp system that affects both the operation of the brake lights and the ability of the vehicle to shift out of park. The brake light switch, which is often located near the brake pedal, serves a dual purpose in many vehicles: it activates the brake lights and also provides a signal to the transmission system that allows the vehicle to be shifted out of park.

If the brake light switch is faulty or fails, it can cause the brake lights not to illuminate when the brake pedal is pressed, resulting in all brake lamps being out. Additionally, since the brake light switch is responsible for enabling the shift interlock mechanism, this failure would also prevent the driver from being able to shift the transmission out of park. Therefore, a malfunctioning brake light switch directly addresses both symptoms of the complaint.

Understanding this connection between the brake light function and the transmission interlock system helps identify the brake light switch as the likely cause of the customer's issues.