2003 Ford Expedition 4x4 with just under 139K miles. 4H and 4L lights flash at the same time - 3 flashes and then stops for 2 minutes. Then flash 3 times again. Vehicle runs fine and no strange noises. The winshield washer light also has been coming on and the reservoir is full. Initially thought it was a couple of wires grounding out in the dash assembly. Now thinking it might be the transmission.