DTC P1706: Park/Neutral Position Switch - Circuit Malfunction : Description
WARNING: This page is about a different car, the 2003 Nissan Pathfinder. 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 circuit (the "ON" signal) exists. The PNP switch assembly also includes a transmission range switch to detect gear position.