apparently they have a DPF filter, and every so often this gets clogged up and your DPF light comes on. In the manual it says to drive at above 37.5mph until the light goes out. So I did but after my third trip up and down the A45 I took it into Nissan. Apparently they can't tell how long or how far you need to drive for and you have to drive at high speeds without stopping. So I tomorrow I have to spend £90 letting them change my DPF filter as if I continue to drive it with the light on, I will damage the the car and it will cost in excess of £2k. They can't tell me how long before this happens again either.
The moral of this story? Unless you drive in excess of 12-15000 miles per year, do not have a diesel