03 Ford expedition have where 4x4 lights will flash on dash

Hello, That means that your 4x4 system will not function, even if you switch it on. You can scan the vehicle for trouble codes to identify what issue the computer has recognized, and this may range from a bad transfer case shift motor, control module, bad wire, switch or connection. In any case, scanning will get you going in the right direction, but remember that the scan tool doesn't tell you what is wrong, it tells you what was noticed.