Check the brake sensor wire on the top of the brake pedal and see if it is broke. On my 01 Auto the wire broke and did the same thing. I was able to fix it myself
2015 Mustang GT 6 Speed - stock.....for now.
SOLD - 2004 Mustang GT 5 speed-Flowmaster mufflers, o/r x-pipe, Delta Force Commando Tuned, 3.73 Ford Racing Rear end gear, Roush Shifter, Roush CAI, Professional Products 75mm Throttle Body and plenum, Steeda Underdrive Pullies, H&R Super Sport Springs(no isolators), MM C&C Plates, Tokico D-Spec Adjustable Shocks, Steeda X2 Ball Joints, UPR Tubular lower control arms, Mach 1 Chin Spoiler, Mach 1 Grill Delete