My od light off flashes when im driving what can i do

Here are some suggestions from another forum. You will probably have to take to a shop and have the codes read on the tranny to be 100% sure what the issue is. 1). Check fuse 23. Wiggle it around, make sure it's in tight and not melted. If that's shorting out or loose it'll cause unholy hell. 2). You have a flaky GEM module, probably water leaking into it. Many 97-10 Expeditions get the dreaded "bottom of the windshiled" leak which conveniently fills up the computer with water. 3). A short in a wire in the control stalk. 4). Bad speed sensor at the tail of the transmission (but he thinks this is an Explorer problem) 5). This requires a follow-up question: Does the blinking happen more frequently the longer the truck has been driven? If yes, the transmission is overheating, probably a bad torque converter. That hard shift is the torque converter failing. Torque converters will sometimes only start to show failure under load and when heated up. There's no trans temp gauge on the Expy, so you're not going to know it's cooking itself to death until the transmission fails suddenly. 6). You've got a bad solenoid somewhere in the transmission that's not working within tolerances, probably only after getting heated up. Look here... http://www.alldatadiy.com/techtips/Ford/20050317d.html Again, though, this will not dump an error code to the OBD II. The error code only goes so far as to blink the OD light with a code.