BMW Cars 1999-06

Operation Repair Guide


The Engine Coolant Temperature (ECT) sensor is referred to as an Negative Temperature Coefficient (NTC) type sensor. This means as the temperature increases, electrical resistance of the sensor decreases. The Engine Control Module (ECM) constantly monitors the value received from the ECT sensor. This information is used to determine the engine's fuel mixture requirements to maintain good driveability from a cold start up to normal operating temperature. The ECM controls the fuel mixture by controlling the amount of time the fuel injectors are activated.

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Fig. Location of the ECT sensor

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Fig. The resistance of the engine coolant sensor for the gauge is shown above. The values change as the temperature changes

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Fig. The Engine Coolant Temperature (ECT) sensor's resistance decreases rapidly as the coolant temperature increases as shown in this graph of the Engine Control Modules' ECT sensor® ©2001- 2020  AutoZone, Inc. All Rights Reserved.