Disconnected the battery post to clean it put it back on now my radio won't turn on I have a 2007 ford fusion

When you changed the battery ,the radio read it as being stolen and placed a code lock into the system. This code can be obtained from the ford dealer if you can provide proof of ownership which you can enter into the radio via the control knobs. IT has nothing to do with fault codes but seeing as to how you have disconnected the battery often you may have to use a code reader to reset the CPU to obtain proper performance again. If you are doubtful as to how to set the code have the dealer service centre do it for you and write down the code in the owners hand book for the next time.

I know this is an old post but may help others

The PCM in my 2006 Ford Fusion is below the battery against the firewall.

You will need to remove the bracket holding the battery, the battery, and the tray that the battery rests on.

The PCM is held to the firewall with 4 bolts and I believe they are 10mm. Remove plugs and unbolt.

Open bleeder valve & push caliper piston, in as
you rotate piston to screw in parking brake

Do this by hand,only use a clamp on the front calipers

Take it back to whomever worked on it

No idea what your referring to without seeing the car

It sounds like you have a dead battery. have it tested.

As with many newr cars, Your radio probably had a security code which is required to reset it after the radio is removed or power was disconnected from it. You probably have the code written somewhere in your new car paperwork. If not, contact your dealer. They can probably guide you through resetting the code.

Its possible that recently disconnected the battery and the LOCK CODE needed re-enter.

Check your owners manual to the procedure.

Good luck.

on the back of the radio itself is a mini fuse next to where the wiring harness plugs in ....i bet this is the problem

YOU MAY NEED THE RADIO CODE. IF YOU DON'T
HAVE IT PULL RADIO AND READ SERIAL NO. TO
DEALER FOR CODE. IF I PULL BATTERY CABLE
ON MY ACCORD I HAVE TO RESET THE CODE.

I was told by the Ford dealership that I had to replace the entire radio. This is also happening with my Ford Fusion (2007). I opted not to replace w/ the same radio because what if it happens again?? My lights came back after some time, but who knows how long they will last.