I think you posted on the FB group, but I'll reply here as well. P0A0A is the interlock. There is a little jumper wire at many or all the high voltage connectors. It has nothing to do with the high voltage connection itself, but is part of a daisy chain of connections that goes from connector to conntector that just checks that all the high voltage connections are secure. Lets say you have a loose connection. This little interconnect jumper would disconnect before the high voltage connection would.
For example, if you lean the rear seat forward and pull the safety disconnect, look at the connector side of it. You will see two little pins close together. They plug into a little connector next to the high voltage connector. If the disconnect were to come lose, these little connectors would be first to disconnect, breaking the chain of connections and then you would get a P0A0A error.
My experience was when I had a contactor fail in the upper battery pack. I had originally sent it to the dealer to diagnose it. In their meddling with the car, they broke the clamping mechanism built into the high voltage connector that is at the driver's side rear tire. So after I fixed the real problem, the failed contactor, I got a P0A0A error. At the rear of the car, there are 5 interconnect points that I know of. 1) the service disconnect behind the rear seat that I already spoke of. 2) The service disconnect by the passenger side rear tire. 3) The high voltage connector at the driver's side rear tire. 4) The high voltage connector in front of the lower battery pack, under the car, and in the center. 5) You have to remove some plastic, but next to the rear service disconnect, there is a high voltage connector that is under an orange plastic cover. That cover has interconnect pins on it and is in the loop.
If any of these connectors are not fully, and I mean fully, seated, you will likely get a P0A0A error. In my case, I had to fabricate a clamping mechanism to secure the driver's side high voltage connector. I spent some time with it and it has been working fine for the past year. One thing that people do on occasion, is pull the service disconnect but don't actually push it back in all the way. That will give a P0A0A as well.
One of the first TSBs on the Focus Electric was that over time, some of these interconnect connectors would oxidize or otherwise corrode so Ford put out instructions to put dielectric grease (I think) on all these interconnection points...not the high voltage connection...just the interconnect connections. So as you inspect, you should see some clear grease on each of these.
If you had rodents chew wires, it is possible that they got one of the interconnect wires, but I'd say that is less likely since the wire for all of these that goes from connector to connector is within the battery itself. The one thing I do not know is if the interconnects under the front hood are in this same loop as the rear battery. If that were the case, then a wire would have to go from front to back, but somehow I doubt it. If the P0A0A belongs to the BECM, which is in the rear battery, I would think that the issue is simply one of your connectors is loose.
One thing to note...the high voltage connectors under the car at the lower battery and the one at the driver side rear tire are a little brittle. They are easy to break. The Ford Dealer broke both of mine. Fortunately, the lower battery one is still serviceable. But as I cleaned up the driver side rear tire connector, I think some of it broke off in my hands. So if you are checking, do so carefully. You might try just seeing if you can wiggle the connection significantly; and if it moves a mm in any direction, then you might try just pushing it in firmly and seeing if the problem goes away. If it does go away, then you need to go back and figure out why it is loose because you don't want that happening while you are driving.
