Sienna XLE lost all electrical - Is it cooked?

I started the car one morning and the belts screamed at me, and the engine raced. When I went to turn off the engine, it continued to run after the key was turned off. I turned the key back on, and tried to turn off again. Finally, the engine slowed and clumped down to a stop, and then smoke poured out from under the hood. An hour later, when I was brave enough to look inside with my husband, we saw the neutral line to the battery was melted entirely. Couldn’t see any broken/melted belts or anything else apparently wrong except that neutral cable. But the car has no electric connection now, nothing will turn on at all. Any suggestions? Do we think I need just a battery/cable replacement, or did I cook the entire computer, etc?

You definitly have more problems than just the cable. You must find out why the problem occured in the first place,probably needs a battery can’t say about the computer but I feel good that it will be ok (polarity was not reversed) I would say $400.00 to start.

Inspect the fusible links to begin with. After that, you might consider the possiblity of a starter motor hanging up; either due to a bad starter or an electrical fault such as a faulty ignition switch that is keeping the starter motor engaged.

I assume when you say your neutral lead burned up you mean the hot lead. While the wiring in your house has a AC neutral lead, vehicles only have a hot and ground lead from the battery. I’m not sure what caused this trouble unless the hot wire from the battery shorted to ground somehow. Unless something happened with the alternator the other things in the car should be ok.

I did wonder myself if it was technicaly correct to call any of the leads from the battery, neutral (my conclusion was that it was not correct but I answered as if one of the cables melted)In house wiring neutral is just that,neutral,what would be the OP’s reasoning to call any of the cables from the battery neutral? neither fit this label.

My conclusion about the melting was continuous high amp draw from a designed load not from a short,the continuing to run info lead me down this path. Does continue to run mean continue to crank? that what I thought.

Any bets that the OP was/is a house electrican?

Thanks to all you who have replied. I find your suggestions/analysis very helpful and instructive. I did in fact mean the ground lead, and just didn’t know the correct terminology. Sorry. I have little knowledge of auto engines, or house electrician either.
I am using all your suggestions to help me discuss this with a mechanic and make informed decisions about the next steps.
Again, thanks, and I’ll post what happens.

I’m glad to hear you find it helpful. All of us here try to provide good help to folks that ask for it.

So it was the ground lead that burned up. That seems real strange to me unless it was previously damaged somehow but even then it doesn’t seem it could cause the trouble you had. The only thing I can think of that may do that kind of thing is the positive battery post shorting to the hood. This would cause all the current to flow through the ground lead only. Did the hood get damaged at all or is there any signs of damage under the hood above the positive post?

Turns out that all they had to replace was the starter motor and the cables to the battery. We were very happy to hear that the ignition switch, battery and computer were all good.
Thanks to everyone for their input and help. I’ll definately be posting future questions about my cars here!!!