DTC P1815 Manual Mode Switch: Description
WARNING: This page is about a different car, the 2008 Infiniti M45 and 2008 Infiniti M35. However, it is still accessible from the selected car via links, so may be relevant.
Manual mode switch is installed in A/T device. It sends manual mode switch, shift up and shift down switch signals to TCM.
TCM sends the switch signals to combination meters. By CAN communication line. Then manual mode switch position is indicated on the A/T indicator. For inspection, refer to "A/T INDICATOR CIRCUIT ".