What is this part and how to fix it.

If you trace the wires, you can likely just splice in some new wires...

 

looks like it’s your engine wire harness. You’ll have to replace the wire harness to where it stops at the connector.

Or you can try this.

 

Looks to be going to fuel injector on cylinder #1. I would solder in wire of at least the same gauge, seal with shrink tube and electrical tape.

You should also do what you can to prevent a reoccurrence, say get it into a secure garage, or at the least: set traps, peppermint oil or irish spring soap chunks, ultrasonic noise makers, whatever you can do. And for sure mesh off the cabin air intake ASAP.

What's your situation, near some woods, parked outside, or?

 

looks to be it since I notice this is the area that was damage on your vehicle

 

I just looked at where the fuel injector was chewed at, it looks deep in there, not sure there’s much wire exposed to be soldering it together. Best thing is to replace it and park inside the garage where rats can’t get in the engine compartment.

 

The location is right above fuel injector no. 1. The wiring diagram shows the wire color for injector no. 1 as yellow, which seems to match the picture. I'd say the identification has been made.

Replacing the entire harness is one (expensive, and laborious) option. Repairing it is another option. We have quite good posts on PriusChat for "wire harness repair" already, that you can find with a search.

When the damage is right next to the connector like that, the repair is made by obtaining a repair terminal, which will replace the terminal in that connector housing and comes with a short length of new wire attached to it. You join that length of new wire to the original undamaged wire a little ways back from the damage.

You find the part number of the proper repair terminal by looking it up in the wiring diagram as in this example. (Or, your Toyota dealer parts counter person can do that for you.)

Toyota, like other car, boat, and plane manufacturers, won't use solder to join wiring that vibrates. Toyota repairs will use a crimped parallel splice (not a butt splice, which for some reason is what you mostly find in consumer auto parts stores). As you saw in the example above the size/color/Toyota part number of the Toyota parallel splice to be used is also shown in the wiring diagram alongside the repair terminal part number.

The finished splice is sealed with heat-shrink tubing containing a sealant.

 

I've got a few

 

Yikes, this is what a rat did to our washer reservoir cap. We were lucky that no wires were chewed on.

And inside the house, chewed right through an ethernet cable running through an attic.

SM-G781V ?

 

Rat traps, cats, snakes... poison....

 

follow what @ChapmanF said, try to find one with the fuel injector connector with the wires long enough to crimp and heat shrink onto your original wire harness.

 

Hold the phone. That one is the light blue one here, runs all 'round the engine compartment, through two different firewall grommets into the instrument panel, includes the fusebox (ask some folks here how fun is removing the fusebox) and so on.

But I don't think it's the one you want. The injector connectors belong to the green one, just "Engine Wire".



Even that one would be tedious to replace, and faster to repair if only that one place is damaged.

 

doesn’t help that the Prius has tight space with no room to work in there I replaced the fuel injector wire harness on the Yukon due to a rat chewing on them and there was so much room. Then the XT5 was a POS but was doable since it’s a small section of the wire harness of the fuel injector that connects to the main wire harness. I wish the Prius was the same so you don’t have to replace the whole wire harness and just a section of it.

 

I'd second the poison choice. We have bait boxes setup on each side of the house and I made sure to replace the bait last year. Thankfully the bait is inexpensive, but in terms of future car headaches, it'll definitely keep those headaches to a minimum for sure.

 

Glue traps (the large rat sized ones), work well. Though sometimes I don't check them often enough, only skeletal remains, or a mass of fur and bones.

SM-G781V ?