Electice cord damage

Pretty easy to replace, just follow it back to the junction box. All/most of the splices should be made there. You may have to remove a portion of the underbelly to gain access. You can also splice any broken wires where it was damaged. I would replace the cord. When the damage was done you may have blown a fuse or two in the tow vehicle if the wires grounded or arced when damaged resulting in the lights not working.

It's possible that the internal conductors are broken even though the outside jacket of the cord looks ok. I'd replace the cord.

Please see any new replies to your question in the other post you made.
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Barney