2007 ford five hundred i changed both rear hub assemblys and changed rear sensors now throwing codes C1998 and C1999 how to fix !!!!

I might be guessing you left battery connected when doing repair you can try disconnecting batt. for a few hours and reconnect , see if that will reset comp. if not A scanner will be needed c 1998 Module calibration not complete ,this occurs when tampering with the ABS sensors or components , abs module ,steering position sensor , steering components , or instrument panel ,, if you get a scanner see if it has ABS module calibration that may come in handy If you ever need it , ,,when you have batt disconnected ,if there is an adjuster on sensor unit or if its just on a flange you can try adj sensor just a bit closer not touching to read speed better , always check connections to sensors { it should always be a must to look for any kind of damage or loose conn. to and from any part of units you are repairing ,including wiring} and you should also check any recalls from ford they had a lot on these vehicles{not that you may want to go that rout you could be without ride for a bit or they might fix ? something you would have to check into ! } check with advance auto on c 1999

If the light comes on when you start moving then you have a mechanical fault. Check the rings on the axels or where ever the wheel speed is being picked up, make sure all the sensors are installed correctly and that there is no damage to the pick up wheels