You have a false contact due to the crash !.
Now you have to try to find where is the false contact.
It can be :
A wire into the serial (DB9) connector;
A pin into the connector;
If it is a pin connector problem, you should see a pin in bad shape.
If no, it is probably a wire connection into the connector....
So you will have to open the wheel, carrefully, note every part you remove and you will probably need to do a welding on a wire.
You can also change the connector, you will found it in every good electronic shop.
Good luck.