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Lotus Service Notes Section EMN
Page 11
EMN.8 - ENGINE COOLANT TEMPERATURE (ECT) SENSOR
The ECM requires a coolant temperature input signal in order to increase fuel delivery and maintain
driveability during the cold running and warm-up phase. The signal from this sensor is used for many different
parameters within the engine management system to control and switch various components dependent on
engine temperature.
The sensor is a thermistor (a resistor which changes value with temperature) mounted in the outlet
junction pipe at the flywheel end front side of the engine. Note that the ECT sensor has a brown body and
harness connector and is mounted horizontally. This should not be confused with the water temperature gauge
sender which is fitted in the same pipe, but has a blue body and harness connector and is mounted vertically
from below. Low coolant temperature produces a high resistance, whereas high temperature causes low
resistance. At normal running temperature, the resistance will be approximately 300 - 400 ohms.
This data is also used to control the radiator fan, which is switched on by the ECM at a rising coolant
temperature of 102°C, and switched off on falling temperature at 96°C.
If the ECM receives a signal voltage outside of the acceptable range, a default setting equating to 60°C
will be substituted, and the cooling fan energised.
To replace the sensor, disconnect the harness plug, and position a container to catch the escaping cool-
ant when the sensor is removed. Unscrew the sensor from the junction pipe. Clean the threads of the pipe and
sensor before applying Teflon tape to the sensor thread and screwing into the pipe. Tighten to 6 Nm. Refit the
harness plug, and top up with coolant (see Cooling Section KF).
If the ECM detects a coolant sensor open circuit, a default value of 60°C will be substituted, and will be
displayed on the 'Lotus Check' scanner tool in Live Data. Sensor faults may cause several symptoms including
poor starting, fast idle speed, poor fuel consumption and cooling fans running continuously.
Engine Coolant
Temperature
(ECT) sensor
- Brown
Coolant temperature
gauge sender
- Blue
em204