1. Check the output signal voltage of coolant temperature sensor:

Install the coolant temperature sensor, the sensor wire connector plugged in, when the ignition switch is in the ON position, from the sensor wire connector THW terminal (Toyota) or from the ECU connector THW terminal and E2 test sensor output voltage signal (for Beijing Cherokee is the sensor wire connector B terminal or from the ECU wire connector “2” terminal to measure the voltage between the terminal and ground)

Toyota car THW and E2 terminal voltage at 80C should be 0.25 ~ 1.0V, the measured voltage value should be inversely proportional to the coolant temperature change. When the sensor harness disconnected, such as from the ECU wire connector “2” terminal (Beijing Cherokee) on the test voltage value, ignition switch open, should be about 5V.

When the coolant sensor is disconnected (high resistance), it will cause the ECU to detect the temperature too low, resulting in poor fuel economy and engine overheating; when the sensor is shorted (low resistance), it will cause the ECU to detect the temperature too high.

2, Coolant temperature sensor resistance check:

(1) Check on the car: ignition switch in the OFF position, remove the coolant temperature sensor wire connector, use a multimeter ohmmeter to test the resistance of the sensor terminals, the resistance value is inversely proportional to the temperature change, the resistance value should be less than 1kQ in the hot engine.

(2) single check: unplug the coolant temperature sensor wire connector, and then remove the sensor from the engine; coolant temperature sensor in the beaker of coolant, heating the coolant in the cup, and at the same time with a multimeter defeat to measure the resistance between the two terminals of the sensor in different coolant temperature conditions.

If the measured value is compared to a standard, the sensor should be replaced if it does not meet the standard.