DTC P1816: PNP Switch (M/T): Description
WARNING: This page is about a different car, the 2011 Suzuki Equator. However, it is still accessible from the selected car via links, so may be relevant.
The M/T PNP switch signals neutral position to the transfer control unit. DTC P1816 will set when the M/T PNP switch signal is malfunctioning.