DTC P1706: Park/Neutral Position Switch: Description
WARNING: This page is about a different car, the 2002 Nissan Pathfinder and 2002 Infiniti QX4. However, it is still accessible from the selected car via links, so may be relevant.
When the gear position is "P" or "N", Park/Neutral Position (PNP) switch is on. ECM detects the position because the continuity of the line (the "on" signal) exists. The PNP switch assembly also includes a transmission range switch to detect gear position.