DTC P0850-29: Park/Neutral Switch Input Circuit - Signal invalid: Action

WARNING: This page is about a different car, the 2018 Jaguar XF, 2017 Jaguar XF, and 2016 Jaguar XF. However, it is still accessible from the selected car via links, so may be relevant.

Check the integrity of the emergency park release. Rectify as necessary
Check the integrity of the parklock mechanism. Using the Jaguar Land Rover approved diagnostic equipment, clear the DTCs and road test the vehicle. Check the parklock mechanism by engaging and disengaging the parklock several times. Rectify as necessary
Using the Jaguar Land Rover approved diagnostic equipment, clear the DTCs and retest. If the fault persists, install a new transmission control module