Fixing "stuck" brake lights on a Honda.
If you are the owner of a Honda/Acura and you find that your brake lights won't turn off - even with the key out and the ignition off - you will be pleased to find that the remedy is usually simple and cheap. When you press down on the brake pedal, a bumper on the top of the pedal assembly moves away from a plunger in the brake light switch. When the spring-loaded brake light switch plunger is free to push out, the brake light circuit is opened and the brake lights come on.
Diagnosing the problem: First, look on the floorboard beneath the pedals. You will almost certainly find bits of blue or yellowish rubber that is broken and dry. These are the remnants of the brake pedal switch bumper. When age and heat get the best of the bumper, it cracks and falls out of the hole that seats it. With no bumper in place, the plunger on the brake light switch has nothing to keep it in, so the circuit remains open as the plunger extends freely through the empty hole. To confirm this, slide your hand up along the brake pedal until you feel the empty hole.
Fixing the problem: Fixing the problem yourself is relatively simple. First, you can go to any auto parts store or Honda dealership and ask for a brake pedal switch bumper. Auto parts stores will sell an assortment for less than $5. Just ask the parts specialist for a "rubber bumper assortment". The assortment will come with a number of bumpers, but the one that you will need will be flanged with a flat, round top.
You will need your engine running (to maintain vacuum to the brake system). Depress the brake pedal with one hand and then, with the other hand, slide the bumper up the brake pedal while feeling around for its home. The flat portion of the bumper should be facing you/the rear of the vehicle). When you get the flange part in, push hard to get it to seat properly. Sometimes universal bumpers are a little too large to fit, so clipping a little rubber off the flange can help. When the bumper is in place, release the brake and the plunger will press against the new part.
Other possible solutions: A broken rubber bumper will be the cause of almost all Honda brake light issues, but sometimes a broken brake light switch is the culprit. If you use your hand to feel up along the brake pedal and the rubber bumper is in place, depress the pedal and manually push the plunger on the brake light switch. Have an assistant check for proper operation of the brake lights. Sometimes the plungers stick and require a bit of lubrication, but other times the spring inside the switch assembly can break. Most switches are only $10-$30 and fairly easy to replace. First, unplug the switch and loosen the adjustment nut with an 18mm wrench. Once the adjustment nut is backed off of the mounting plate, the threaded brake light switch can generally be unscrewed by hand and removed.