Trouble shooting brake light on instrument panel. Checked for any leaks, none found. Master cylinder full. With key off pedal travels shorter distance with every press and holds steady. With engine on pedal holds pressure, doesn't sink to the floor. Took it out and slammed on the breaks, ABS still works, didn't lock up or pull dramatically. Is there anything else I should do before I tear into the brake lines and change this out???

 

Parking brake switch.

 

When I engage the parking brake the light get brighter, and then dims when I release it. The only way to get the light to go out is to disconnect the Combination Valve connector.