DTC P2420: Evaporative Emission System Switching Valve Control Circuit High [08/2015 - 08/2018]: Description
WARNING: This page is about a different car, the 2018 Toyota Sequoia, 2017 Toyota Sequoia, and 2016 Toyota Sequoia. However, it is still accessible from the selected car via links, so may be relevant.
The description can be found in the EVAP (Evaporative Emission) System Refer to: