Coolant Temperature Sensor

The coolant temperature sensor is located in the cylinder head. This sensor provides ECU with an engine temperature signal.

If sensor reads a high engine temperature (with cooling system operating properly), this would indicate combustion temperature that is too high. The control unit would then enrichen the mixture (to the point allowed by the oxygen sensor and air mass meter signals) to lower combustion and engine temperature. On Volvo models, this sensor also operates the temperature gauge.