Power Mirror Switch Test/Replacement

Carefully pry the switch panel out from the dashboard.
Disconnect the 10P connector (A) from the power mirror switch (B).

Fig 1: Identifying Power Mirror Switch And 10P Connector
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Check for continuity between the terminals in each switch position (see Fig 2).
Mirror Switch:

Fig 2: Checking For Continuity Between Terminals In Each Switch Position - Mirror Switch
Courtesy of AMERICAN HONDA MOTOR CO., INC.
If the continuity is not as specified, replace the power mirror switch.