Nissan Serena Engine Management Temp Sensors Available Here. Your vehicle’s engine management temp sensors measure the temperature of your coolant as it circulates through the engine. They send data to the ECU so it can determine what adjustments to make. They also may send messages to your cooling fan and temperature gauge. Sensors can fail due to moisture, dirt or vibrations; any problem with them can quickly lead to an overheated engine. Your engine needs more fuel when it’s cold and less when it’s fully warmed up. A bad sensor can send a permanent cold signal to the ECU, resulting in more fuel being used than is necessary plus black smoke coming from the exhaust pipe. Faulty engine management temp sensors need to be replaced immediately.