BMW 13621709967 Water Temperature Sensor

The Engine Coolant Temperature (ECT) sensor is a Negative Temperature Coefficient (NTC) type sensor that measures the temperature of the engine coolant. As the temperature increases, the electrical resistance of the sensor decreases. The Engine Control Module (ECM) constantly monitors the value received from the ECT sensor to determine the engine's fuel mixture requirements. This information is used to maintain good driveability from a cold start up to normal operating temperature. The ECM controls the fuel mixture by controlling the activation of the fuel injectors. To test the ECT sensor, use a BMW service tester or a suitable Data Scan Tool (OST) to check for faults and read the values of the components. If this equipment is not available, you can proceed with the following steps. First, unplug the sensor and measure the coolant temperature as close as possible to the sensor location. Then, measure the resistance between the terminals of the sensor and compare the results to a chart. With the ignition switch ON, the sensor should receive 5 volts at one of the connector terminals. The other terminal is the return signal to the control unit and should not be used for voltmeter ground. To remove and install the ECT sensor, follow the specific instructions for your engine model. It is important to allow the engine to cool before removing the sensor to avoid burns. Unplug the electrical connector, use a 12 point 22mm thin wall deep well socket to remove the sensor by turning it counterclockwise. Remove the sensor along with its sealing washer. When installing the sensor, use a new sealing washer and tighten it to 10 ft. lbs. (14 Nm).

The engine coolant temperature gauge uses a heat-sensitive sending unit to transmit an electrical signal to the gauge. The sending unit is a heat-sensitive variable resistor located on or near the cylinder head and threads into an engine coolant passage.