I have been dealing with this problem for years. The red brake light on the dash comes on only once in a great while and doesn't save a code. The light is now coming on more often. the only time it comes on is when the truck is on cruise and usually going up an incline. the fluid level in the brake master cylinder is at max., the cylinder cap has been replaced and the parking brake has been pulled up on after the light has gone on. The light goes off when the truck is turned off and no code is stored. The dodge dealer I've been working with for years about this problem told me the other day when I called and said the light is now on please read the code. we're to busy today bring it in tomorrow. The problem was gone when the truck is turned off.