The link for a previous answer provided by Barbara H above indicates that the F DL error code on a washer that you seem to be describing indicates a problem with the door lock assembly. Based on your details, it is likely that the troubleshooting described by Mark T in that previous answer may help you with this problem. Unplug the washer and check the wire harness connection on the door lock assembly and the control board. If the wiring connections are okay then the door lock assembly will likely need to be replaced to fix this problem.
If you need more help, reply with additional details and the full model number of your washer.
If you do not feel confident repairing this problem yourself, then you can have it repaired at your home by a Sears technician. Here is a link for the website:
Sears Home Services