It's possible the switch is bad. Test it for continuity with an Ohm meter. Never assume a new part is good or bad, always test first if there is a problem. You may have a short in the harness. Why did you replace the switch, same problem?
the switch is defective, when it is replaced the lights will only go on when brake pedal is engaged. also if the switch doesnt work you will not be able to shift into any gear, it will jam the sensor.
Opening up the front panel underneath your steering wheel will allow you to wiggle the switch and the shifter usually begins to return to gear. If the switch looks like it is good but still brake lights stay on, you need a new switch that one is defective.