What is this?

[jumpingjackdan]

Hi, please see picture below. Took the rocker cover off brothers car, zetec-s mk5 fiesta. In the middle between the spark plugs there looks to be some kind of sensor (yellow), putting it back together the plug snapped (it was very brittle). Anyone know what it is, the Haynes manual he has doesn't have this engine as it was from the focus and put in the zetec-s. I will need to solder a new bit on but Im not sure what plug I will need. Ideas?

[jumpingjackdan]

Thanks, I thought it would be something to do with temperature. Where can I get the plug to solder onto the cable? The actual sensor is ok.