A:Answer Hi Okienana,
For your 2012 Toyota Avalon you will need: the XAV-AX1000 unit, a Toyota-compatible dash kit, a wiring harness adapter, an antenna adapter, possible steering wheel control interface, and Sony strongly recommends installation by a qualified, professional installer due to the variables involved with different makes and models. They provide wire color/function documentation for their harness, but not for the vehicle's wiring.
Best regards,
Eliab