What is the likely cause of brake lights remaining on continuously?

The brake lights remaining on continuously is most likely due to a stuck brake light switch. The brake light switch is a critical component that activates the brake lights when the brake pedal is pressed. When functioning properly, the switch should close when the pedal is pressed and open when it's released, allowing the lights to turn off. If the brake light switch becomes stuck in the closed position, it will cause the brake lights to remain illuminated even when the pedal is not engaged.

This malfunction can occur due to a mechanical failure within the switch itself or due to misalignment, preventing it from returning to its open position after the brake pedal is released. Troubleshooting this issue would typically start with inspecting the switch for proper operation and alignment.

In contrast, a blown fuse would typically lead to the brake lights not functioning at all, rather than being continuously on. The right brake fluid level or type being used would not affect the operation of the brake lights since brake fluid is involved in the hydraulic system for braking, not in powering the lights. Similarly, the choice of brake light bulbs would also not cause them to remain on continuously, as a correct bulb installation would either function or not function completely based on the integrity of the bulb rather than causing a state of constant illumination.