DTC P1420: Evaporative Emission Canister Small Leak; DTC P1421: Evaporative Emission Canister Gross Leak [11/2016 - 10/2017]: Description
WARNING: This page is about a different car, the 2019 Toyota Highlander, 2018 Toyota Highlander, and 2017 Toyota Highlander. 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 DESCRIPTION