Fiesta TDCi 57 temperature reading is --ºC

[Tangerine]

Hello,

This is my first post as I have only recently acquired my 2007 Fiesta TDCi.

Tonight, I just noticed that the temperature was displayed as --ºC having previously shown it. 

I know that the radio mode is also shown in the same display and a few days ago I installed a Pioneer head unit to replace the Ford 6000CD - mainly to avoid all the wires required to connect my iPod to play music - but I am pretty certain that the temperature was still shown up until yesterday so I don't think that changing the radio caused the problem.

I have read that it could be a fault with the sensor but I have not been able to find a post which shows where the sensor is (maybe now I am registered, there may be photos in the posts which I couldn't see before) but I am wondering if there could be any other cause.

Incidentally, I have the Haynes manual for the right model Fiesta and it doesn't even mention the temperature sensor.

Thanks in advance.

[Tangerine]

Having been confused by images which looked like a brass spark plug and having been unable to see anything like that, I have finally realised that I was looking for the wrong thing. For what it is worth, I think I have found the sensor but it isn't exactly accessible - though with the help of a couple of pairs of forceps, I have ensured that it is fully engaged in the connector.

If anybody could advise me on the simplest way to replace it, I would be very grateful.