Hi Doobie
The code you refer to is listed on here as an 02 sensor however the workshop manual for the D40 makes no mention of this code and there is no 02 sensor fitted to the Euro3 or 4 models.
If you want help you'll have to tell us a bit more. In this thread tell us what model you have, what age, mileage, what symptoms are you experiencing and how you extracted this code.
It would be appreciated if you visited the 'Introduce Yourself' section and tell us more about yourself and your Navara. You'll receive a warm welcome and more members will be willing to chip in.