Hi, based on the maintenance manual, the code P1815 may appear under below two conditions:
• TCM monitors manual mode, non manual mode, up or down switch signal, and detects as irregular when impossible
input pattern occurs 2 second or more.
• Shift up/down signal of paddle shifter continuously remains ON for 60 seconds.
The code may be caused by below reasons:
• Harness or connectors (These switches circuit is open or shorted.)
• Mode select switch (Into A/T shift selector)
• Position select switch (Into A/T shift selector)
• Paddle shifter
Please refer to the maintenance manual to fix it. Thanks!