My brake warning light came on in the Challenger. The car has been sitting since August as I had the column rebuilt, finally fired it up over the weekend and the brake warning light is on, and wasn't before. I can't find any leaks and they seem to be fine just inching forward and back. I pulled the Master cylinder cover and fluid level is fine. What triggers this warning, fluid level or pressure, both? Is it possible it's a bad sending unit?