DTC P2610: ECM/PCM Internal Engine Off Timer Performance: Description
WARNING: This page is about a different car, the 2006 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.
The soak timer is built into the ECM. To ensure that the Evaporative Emission (EVAP) monitor values will be accurate, the soak timer counts 5 hours (+-15 minutes) from when the ignition switch is turned OFF. This allows the fuel to cool down, which stabilizes the Fuel Tank Pressure (FTP). When approximately 5 hours have passed, the ECM turns ON.