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

NOTE: This DTC may be set following a valid emergency park release operation. Establish if the emergency park release has been used on this vehicle

Prioritized steps to perform:
Using the Jaguar Land Rover approved diagnostic equipment, check for other transmission DTCs and investigate/rectify those first
If this DTC is set then, using the Jaguar Land Rover approved diagnostic equipment, check if the fault was set while the engine was running or not running
If the fault was set when engine WAS running: cycle service park release mechanism by hand to ensure it is not sticking. Return service park release mechanism to the normal position. Clear DTCs. Road test the vehicle up to a normal operating temperature while engaging and disengaging Park with gear selector. Re-check DTCs. If fault persists raise a Technical Assist (TA) for further support
If the fault was set when engine WAS NOT running : if the emergency park release WAS used, this would indicate that the use of the emergency park release is the most likely cause. Establish if this has been used. If so, clear DTC and retest. If fault does not reoccur then no further action is required. If the emergency park release WAS NOT used or if status not known, then check the integrity of the service park release mechanism. Check that the park position sensor mounting is secured at the correct torque (6Nm) and rectify as required. To gain access to the park position sensor mounting it is first necessary to remove the ten mounting bolts of the main control valve body and lift the valve body unit from the transmission housing (refer to Automatic Transmission. Removal and Installation. Main Control Valve Body steps 1 to 5).
NOTE: New oil tubes must be installed when the unit is reassembled. The park position sensor is located inside the main casing adjacent to the electrical connector. The sensor is secured to a boss in the main casing with a screw
Clear DTCs. Road test the vehicle up to a normal operating temperature while engaging and disengaging Park with gear selector. Re-check DTCs
If the fault persists, check the transmission fluid level using the Jaguar Land Rover approved diagnostic equipment to run the 9-speed ZF - Automatic Transmission Fluid Level Check Application. Refer to the relevant article of the workshop service information and check the automatic transmission fluid quality For additional information, refer to: TRANSMISSION OIL COLOR CHART .
If the fluid condition is unsatisfactory, raise a Technical Assist (TA) for further support
Refer to the electrical circuit diagrams and check circuit(s) L3 and L4 for short circuit to power, short circuit to ground, open circuit or high resistance. Repair the wiring harness as necessary
If the fault persists, raise a Technical Assist (TA) for further support