Xantia 2.1 Coolant Sensors

[bddeazeley]

I have a 1998 Xantia 2.1 TD which has 2 coolant sensors a blue one and a brown one. I have read on some posts about a 3rd green coolant sensor at the back of the fuel filter housing which apparently is used by the ECU to calculate fuel pump timing. My Xantia does not have this green sensor and where it would be fitted there is a bolt/plug inserted to blank it off. Does anybody have knowledge of what the ECU uses instead of the green coolant sensor as Citroen appear to have changed the design. Many thanks, Brian.