it sounds like the ABS sensor that is in the rear differential housing. remove it and see if it has some metal fragments on it. You can try to clean it, remove the battery negative cables for ten minutes to clear codes and test drive. if this doesnt work replace the sensor. it is the most common trouble unless something is still unplugged or came unplugged because of the accident. in that case check all conections at the front of the vehicle around the ABS assembly which is probably near the left front or right front frame rail. email me with what you find. I used to be a factory Ford Master technician. if you dont find anything play the starving student thing and call the local dealership and see if you can talk them into having the shop foreman pull the codes for free.