The passenger side doors don't always unlock automatically (either through the remote or switch).
The passenger door locks are controlled by the body computer on the Highlander. In this case either the wiring to the passenger door lock motors is compromised, the signal to unlock the doors is lost before it gets to the body computer, or the body computer is faulty. Since this is an intermittent issue, it leans towards a door harness issue The door wiring harnesses need to be checked, especially at the lock motors, to see if the activation signal is present. Door harnesses are susceptible to connection issues especially in flex points where the door opens and closes and in the door harness connection to the main body harness. You may want to enlist he help of a mechanic, such as one from YourMechanic, who will have the tools and training to diagnose this door lock issue.
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