Perhaps P0715? Probably heading in the right direction.
Did you clear codes after your plate switch ? I read you disconnected battery, but did you check to see codes cleared before starting car?
Was there trans fluid on the electrical connection when you first got under the car and unplugged it? That fluid can wick up the cable to the TCM.
You can get a new OE trans plate here for reasonable price, click: conductor plate
Read the first post in this thread: P0715 fix
Read the post #8 to clear codes, important: clear codes
Here is more info you may want to consider: repair service