Airbag light flashes 5 then 1

Code 51 is air bag diagnostic monitor internal thermal fuse is blown. This usually happens when air bags have deployed at some point -- have they? If the air bags have never deployed, you likely have a wiring short to ground in this system that will need to be found and repaired. Only after validating all wiring is OK should you attempt to replace the diagnostic monitor. Seek guidance at a local shop near you: https://repairpal.com/repair-shops/ford-repair-and-service-in-elkridge-maryland