Trying to bring dead 2005 prius back to life

I bought this vehicle in non-running state. Previous owner said the cat got stolen, so he paid out 900 for new cat, then it started running rough. He took it to mechanic who he says replaced the 12v battery and said it probably needed a new traction battery.

I swapped in a reasonably healthy traction battery, but the car won't power up now from the power button on the dash. I can jump it at the jumper point under the hood and it powers up and starts the ice engine, but no dash lights.

I can check the voltage at the 12v battery in the back and it shows 13.5v. At the jumper spot under the hood, I get zero volts.

I would like to get resolve this power up problem as first step, then check the codes.

Any thoughts? Thanks in advance.

 

jumped under hood and got CA799, no engine codes, but dash lights etc. everything shut down when 12v jump battery disconnected, so I am looking at how to get power through from 12v in back to the main panel under the hood. 5 amp fuse on positive terminal of battery is good. The fusible link in the positive terminal looks good, but it's open to the air, looks like the plastic cover on that link got knocked off with the 12v batter change

 

Yes, I started there with the story about new 12v battery. It does look like a new battery. I am going to be on the road today, so may not get back to this until tomorrow now

 

I switched to torque pro lite and it says, Fuel system status: open loop due to insufficient temperature,

then
Secondary air status
no data/not supported.

I think I have several problems. One is the 12v issue. I think the second is in mass air flow sensor or maybe 02 sensor or something like that. Will be easier to work on second once I can start the car up using the smart key. Right now, I have to jump it under the hood.

gonna be on the road today, back at it tomorrow.

Thanks
here is photo of the positive terminal on 12v with the fusible link that looks off to me.

 

photo

 

took the ground loose and the battery reads 5v, so next step is to charge 12v up. Thanks, I was reading inverter voltage and missing the dead battery issue

 

dr prius. If you seach the prius chat, it is mentioned a few times and dismissed as some kind of glitch with dr. prius. I switched to torque lite and not getting ca799.

 

charged up the 12v battery and powered the car up, but I had dr. prius running and I could watch the battery state of charge dropping at a surprising rate, so I disconnected the 12v battery again. It appears something is pulling a lot of juice out of the traction battery when the car powers up. Any ideas? I was going to read codes again, but I was didn't think there was time to mess around with codes because the battery charge was falling so fast.

I plan to put the grid charger back on the traction battery and a 12v charger on the little battery and let them run over night. But with both of the batteries isolated from the vehicle. I just want to keep the batteries in a healthy state until I figure out what is going on with this car.

 

I checked that just now. Both now read the same. about 10.5v I disconnected the ground after checking that and put the 12v charger back on. The draw on the charger with the ground connected is causing the charger to cycle off, like the battery is trying to pull more than the 10 amp rating of the charger. I think my next step is to figure out what is drawing juice out of the 12v battery

 

I have a spare prius battery on the shelf in the garage. I will throw a charge in that one overnight and put it in the car tomorrow and see what happens.

 

swapped in charged battery and it started acting like a prius. I think aside from the dead/defective battery, the vehicle was also out of gas. I filled the tank and I think it's time to get the plates on it and start cleaning it up. It might be good to go after quite a rough patch.

thanks to everyone who helped me get it to this point. I am feeling pretty good right now!