Check brakelight switch at the pedal with a light tester. If it works there but not at the plug at the front kick panel going to the rear body harness, you probably have a bad turn signal switch. Your brakelamps run thru the turn signal switch.
Don't have a testlight right now. Need to grab one. Tested the voltage at the brake light switch on the pedal. 11ish volts with pedal not depressed, 0V (or close to it) with pedal depressed. Ill grab a test light and pop off the kick panel.
