BMW 13621433077 Coolant Temperature Sensor

The engine coolant temperature (ECT) sensor is an NTC (negative temperature coefficient) sensor, which means that as the coolant temperature rises, the resistance through the sensor decreases. The ECM adjusts ignition timing and air/fuel mixture based on the engine coolant temperature, receiving a 5-volt reference voltage. The voltage drop across the sensor changes with variations in coolant temperature and sensor resistance. If the ECT sensor input is faulty or implausible, the MIL illuminates when OBD II fault criteria are exceeded, prompting the ECM to assume a substitute value of 80 degrees Celsius/176 degrees Fahrenheit to maintain engine operation, with ignition timing set to a conservative basic setting. The ECT sensor is located at the left front of the engine near the oil cooler. To replace it, ensure the engine is fully cooled, then disconnect the ECT sensor connector and unscrew the sensor from the cylinder head, being prepared to catch a small amount of coolant. Installation involves reversing the removal process, using a new copper sealing washer, and replacing any lost coolant. After reinstalling, check and clear fault codes from the ECM memory.