Have you got the problem solved? I also have the same DTC code P2002 on my Mondeo 2.0 tdci duratorq -07 but I get it together with P1335 wich is a fault in the EGR System.
The DEF fluid pressure sensor is used to monitor the pressure of the DEF fluid and ensure that it is flowing properly. The DEF Quality sensor is used to monitor the quality of the DEF fluid and ensure that it is meeting the required specifications. All of these sensors are important components of the Cummins diesel engine emissions system. There are 3 sensors associated with the DPF that are used to feed information back to the CDI control unit* (N3/9). The two listed above in post #2, plus the Exhaust back pressure sensor (B60) which is located at the rear of the engine. This monitors the DPF fill level for protection of the turbine & the engine. P2455 – Diesel particulate filter pressure sensor, short to positive or open circuit. This fault code can be caused by several factors, which are listed below: Short circuit in the wiring between the sensor supply voltage (5 volts) and the signal wire; Open circuit on the ground circuit of the sensor; Faulty exhaust gas differential pressure Ford, in their infinite wisdom (?) seem to have changed from using a DP sensor with two hoses to the DPF, to a pressure sensor with just one hose. I can only guess that it is a gauge pressure sensor, and they are assuming the outlet pressure of the DPF is near atmospheric pressure, just a bit of back pressure from the muffler & pipe, that can I'm having a heap of issues, notably low power in low revs and failure to start after filling up with petrol. The only thing I can think of is the purge valve is stuck on, not closing fully, or has a leak (most likely). IVFr.