DTC P2610: ECM / PCM Internal Engine Off Timer Performance [11/2016 - ]: 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 soak timer operates after the power switch is turned off. When a certain amount of time has elapsed after turning the power switch off, the soak timer activates the ECM to perform malfunction checks which can only be performed after the power switch is turned off. The soak timer is built into the ECM.