First rule of Toyota ownership - get a VXDIAG VCX NANO Toyota cable and the matching Techstream software.
Do a search on www.vxdiagshop.com for VCX cable. You want the one that has "Powered for TIS" on it (ie there are different versions for different car brands; the TIS one is for Toyota).
eg: http://www.vxdiagshop.com/wholesale/vxdiag-vcx-nano-for-toyota-wifi-version.html
Techstream is the software that Toyota dealerships use to diagnose cars.
Used with a laptop running Windows (I have Parallels and Windows on my Apple MacBook Pro), Techstream will tell you everything about the car.
Example:
2007 Prius with 148,000km - one of the modules died a while ago.
These error codes indicate a fault in the hybrid battery, particularly in block 7 (ie P3017 indicates block 7... the battery modules are paired into blocks):
You can see how block 7 has a lower voltage than the other blocks, indicating a faulty module.
I had to rebuild/repair the hybrid battery.
www.vxdiagshop.com