The task of the controller includes a calculation of the coolant temperature. It is produced by the voltage drop on the sensor. How correct the sensor reading the coolant temperature directly affects most processes that are controlled by a controller.
Quite often problems arise because of damage to the wires that come to the sensor. There are times when there is a broken wire at the sensor connector. Such problems lead to the fact that the fan is switched on at a low temperature. From the exhaust pipe is black smoke. If a condition exists, the instrument panel warning light "CHECK ENGINE" may not illuminate. The engine in this case, it is better not to turn off, because then he may not start. To move at low speed is still possible.
Problems can arise, if the temperature sensor coolant. To test this sensor, you need to perform simple actions. For starters, disconnect the harness from the sensor. Turn on the ignition. Engaged in circuit testing. When measuring the voltage on terminal "In" to ground should be about 5 V. If the voltage is less than 4.7 V, the connection must be considered unreliable. It's possible that wire is shorted to ground or a short circuit. You also need to check the serviceability of the controller in this case.
Turn off the ignition and measure the resistance between the contact pads of the sensor A and ground. The resistance should not be less than 1 Ohm and no more. If the resistance measures more than 1 Ohm are quite possible wire breakage.
After this you need to disconnect the controller connector and check the resistance, which will be between the sensor contact pads and the contact pads of the controller 45". It should be less than 1 Ohm. If it is greater, then the connection in the stocks unreliable.
Then measure the resistance between ground and contact pads of the sensor. It should not be less than 1 Ohm. If less, then there is a short to ground.
Do a sensor test. Measure the resistance at two values of temperature of cooling liquid. This should be done at cold and hot engine. Resistance must not vary. If there are differences, it is necessary to replace the sensor. If the sensor and circuit are in good condition, then the model checker.
Temperature sensor engine temperature Sensor coolant sensor is an engine temperature (TSG) and is a thermistor, i.e., a semiconductor resistor whose resistance is changed by temperature. The sensor is screwed into a flow pipe for the engine cooling system and is constantly in the flow of coolant.
Most of the temperature sensors is the thermistor usually negative temperature coefficient - in other words, when the temperature increases, the resistance of the measuring elements in such sensors is reduced. In case of any problems associated with temperature measurement for a long time to find where is the engine temperature sensor, usually is not necessary.
Advice 2 : How to check the engine temperature sensor
The sensor temperature of the engine is a thermistor, which changes its resistance depending on temperature. It gives information to the electronic device engine to control the supply of fuel and ignition systems. And how to check?
Malfunction of the engine temperature sensor is manifested as a resistance standard. For example, when engine temperature is 75 OS standard resistance is about 290 Ohms. If the sensor has a resistance of 100 Ohms more that the EFI unit "think" that the engine still not fully warmed up, and will give the cylinders more fuel. And this is usually increased engine rpm.
The sensor is tested after removal from the engine. To do this, remove the air cleaner, pour it in the coolant. Then disconnect sensor electrical connector and Unscrew it from the housing.
Lower the engine in a container of water and heat at a temperature of 90 ° C, turn off and leave to cool in the pot. In parallel, temperature control by means of a special device (thermometer) and take readings with the ohmmeter. If performance is approximately 100-700 Ohms, so everything is in order and if not replace the sensor. Also measure the resistance of the sensor at different values of temperature, namely at a temperature of -10 ° C + / -3 ° C - resistance is 8.2 to 10.5 Kω at 20 ° C + / -3 ° C and 2.3-to 2.7 Ohms, and at 80 ° C + / -3 ° C resistance equal to 0,3-0,36 Ohms. If these data fall outside the standards, then the sensor requires replacement.
Check the engine temperature sensor's resistance with other features described in the instruction manual of the sensor. In any case, do not check the sensor circuit directly on the engine without disconnecting it from the control system, since in this case the risk of damage to the electronic control unit.
Basically, the malfunction of the engine temperature sensor very rare and occurs usually on the machines, which age more than 12 years.