What year of Ford?
What model of Ford?
Does it ever shift into overdrive?
Did this start all of a sudden with no other symptoms?
I will help you with a little more information.
2003 Mercury Mountaineer
Usually shifts fine
Started without any other problems occuring.
You most likely have an issue with a mechanical concern in the transmission. On this model this could mean a servol bore worn out, a band broken or a possibly a valve body issue. The flashing light means there is a code stored in the system related to the transmission. There really is not much that you could do. You could have the codes pulled by a parts store, but this won't tell us much. This transmission had an issue with the servo bore wearing out in the case. There is a repair available to fix this without replacing the case. It will have to be diagnosed by a good tech to know for sure what is wrong. I wish I had better news for you. If you would like to get the codes retrieved (auto parts stores such as Autozone will do this for free) I will be happy to explain the codes and what they may mean. I hope this helps you. If you need anything else, just reply back and I will be happy to assist you more.