P3125 info 304 - damaged wiring harness after inverter/converter pump failure

I accidentally necroed a thread at that location and have pasted my post here (which I believe is the correct place)

I burnt up my inverter/converter cooling pump which then damaged the wiring harness in the main engine room (likely because I pulled an idiot move and replaced the fuse that was blown with a higher amp fuse to limp about a mile after the first fuse blew). I had the pump replaced and the wires going from the fuse box to the pump replaced, since the dealership wanted $4000 to replace the entire wire harness (the rewiring and replacement pump still ran $1000). So now I have the P3125 info 304 code. These are the only codes that it is throwing. It will start, but it shuts down after about 30 seconds. The coolant pump has been verified at the dealership to be in good working.

I was hoping to get some direction on the possibility of repairing this myself. I do not have the funds to drop $4000 on a car that I bought used for $4000 and I would dearly love to continue driving it.

I was confused as to what to disconnect to test this wire and exactly what the procedure would be to test it. Am I checking the wire against the body of the car or am I supposed to check it against the other wires in the bundle? If I do find that it's shorted, how feasible would it be to replace that run of wiring? I looked at some schematics and it seems like a long run from the inverter/converter to the ECU.

Any assistance would be immensely appreciated!