The Diagnostic Trouble Code (DTC) P1884 for a 2002 Land Rover Discovery typically indicates an issue related to the transmission control system, specifically the Transmission Fluid temperature sensor or circuit. This code suggests that the vehicle's engine control module (ECM) has detected an abnormal reading from the sensor, which can affect transmission performance and shifting. It is advisable to check the wiring and connections to the sensor, and if necessary, test or replace the sensor itself to resolve the issue.