autometer oil temp gauge sending unit

• 2022-11-21

Installation position and function of the transmission oil temperature sensor. The transmission oil temperature sensor is installed on the valve plate in the automatic transmission oil pan, which is used to detect the temperature of the automatic transmission hydraulic oil, and serves as the basis for the electronic control unit to control gear shifting, oil pressure and lock up clutch.

Structure and working principle of transmission oil temperature sensor the transmission oil temperature sensor is a negative temperature coefficient semiconductor thermistor. The higher the temperature, the lower the resistance. Refer to the characteristics of negative temperature coefficient thermistor in coolant temperature sensor for the characteristic curve of its resistance changing with temperature. The computer measures the temperature of the hydraulic fluid of the automatic transmission according to the change of its resistance.

Symptoms of the failure of the transmission oil temperature sensor The transmission oil temperature sensor is used to detect the temperature of the hydraulic oil of the automatic transmission, as a basis for the electronic control unit to control gear shifting, oil pressure and lock up clutch. The automatic transmission oil temperature sensor is installed on the control valve to mainly control the high temperature of the transmission. If the transmission oil temperature sensor is broken, it will not detect the temperature of the transmission oil, so it will not be able to provide the oil temperature signal to the transmission computer, which may cause the transmission shift impact. When the transmission oil temperature is higher than 150 ℃, the torque converter will enter the locking condition immediately. If the transmission oil temperature does not drop after 30s, the torque converter will release the locking condition, and the transmission will exit the overdrive. If the oil temperature sensor itself or the harness is short circuited, the data flow will show that the transmission oil temperature is higher than 150 ℃. Therefore, after the oil temperature sensor itself or the harness is short circuited, the torque converter will not enter the locking condition, the transmission will not have an overspeed gear, and the car will not have a high speed.

Effect of signal failure:

1)The torque converter lock up clutch has no adjustment operation and can only be opened or closed; There is no suitable shift pressure, which usually results in difficult shifting.
2)The negative temperature coefficient (NTC) thermistor of transmission oil temperature sensor G93 has a characteristic relationship.
3)As the temperature increases, the sensor resistance decreases.
4)In order to prevent the transmission from overheating, the corresponding countermeasures will be triggered when the transmission oil temperature exceeds the defined range.
5)Countermeasure 1 (about 127 ℃): Use the dynamic shift program (DsP) function to shift the gear at a higher speed. The torque converter lockup clutch is closed earlier and will not be adjusted.
6) Countermeasure 2 (about 150 ℃): the engine torque is reduced.