Error 17664

[dunkymunky]

So, car is throwing up error 17664 intermittently . I know this is engine coolant temperature sensor. Couple of questions:

1. When the car is running, temp guage is working fine, climbs steadily to 90 then stays there, so how can the sensor be broken?

2. Is the sensor under the car, near the front, just right of the centre (as you look at the front of the car)?

3. Can anyone help me out with a part number? Mines a 2005 1.9TDi Highline

Thanks in advance