Engine coolant temperature (ECT) sensor

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2007 Volvo V70, 2006 Volvo V70, 2005 Volvo V70, 2004 Volvo V70, and 2003 Volvo V70. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Engine Coolant Temperature Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

The engine coolant temperature (ECT) sensor checks the temperature of the engine coolant. The temperature of the engine coolant is required so that the engine control module (ECM) can regulate:

the injection period
the idle speed
the engine cooling fan (FC)
the ignition advance
engagement and disengagement of the A/C compressor
diagnostic functions.

The sensor is a negative temperature coefficient (NTC) type which is supplied with power from the control module (signal) and is grounded in the control module.

The resistance in the sensor changes depending on the temperature of the coolant. Depending on the resistance in the sensor, voltage (signal) is transmitted to the engine control module (ECM). The lower the temperature the higher the voltage (high resistance). A high temperature results in low voltage (low resistance).

The engine coolant temperature (ECT) sensor is located beside the thermostat.

The engine control module (ECM) can diagnose the engine coolant temperature sensor. The sensor value can be read off using VIDA.