I've heard not disconnecting the battery can damage the EPAS system. When I installed mine I didn't take any chances, I disconnected the battery and waited half an hour before giving the knuckle a smack to release the tie-rod joint. Apparently doing so with the battery connected can screw up the EPAS system. Here's a link to another member that found out the hard way. http://www.f150forum.com/f7/2011-f-1...problem-97425/
Take this with a grain of salt tho (I am by no means a mechanic), it could totally be something else. Good luck man!