Engine light on on my disco 3

[johnstontp]

Hi I wonder if anybody can help I drive a landrover discovery 3 2.7v6 and I have a engine light that has come on I have checked it with my computer and it is a permanent fault to do with the egr sensor A the fault code was P0405 does anybody know what is wrong is it the sensor or the egr cooler ? And if sensor which one would be very greatful if someone could please help many thanks TP