Transmission Temperature Sensor/Switch: Description and Operation
Sensors
The following sensors are used in the transmission for recording speed, temperature, pressure and distance signals.
- 4 distance sensors (combined in one housing)
- 2 rpm or speed sensors (combined in one housing)
- 2 pressure sensors
- 1 temperature sensor
The distance and speed sensors are connected by a wire harness and are guided outward via the 16-pin transmission connector.
The transmission has two separate wire harnesses due to the design with two chambers with different fluids. A 16 pin harness is installed in the section with gear lube (Mobilube PTX Formula A SAE 75W - 90) and a 20 pin harness in the section with hydraulic oil (Pentosin Gear Oil FFL3).
The pressure sensors (2) are connected to the wire harness, to which the solenoid valves and pressure adjusters are connected. The temperature sensor (3) is connected permanently to the wire harness. This is guided out of the transmission via a 20-pin connector.
The sensors are all located in the transmission. Sensors cannot be removed or installed from outside.
Distance sensors
The distance sensor unit (also called "sensor tower") is used for recording the position of each individual shift rod (1). It is designed as an assembly, made up of 4 integrated absolute distance sensors.
Each shift rod (1) is assigned a sensor, which converts the linear movement of the shift rod into a distance-proportional PWM signal. Other functional components of the distance sensor unit include four associated sensor magnets (2) on the shift rods. The supply voltage for the distance sensors is 5 V.
The diagnostic system checks the sensor as follows:
- Short circuit to ground
- Short circuit to supply voltage
- Open circuit in line
- Signal plausibility
Speed sensors
The speed sensors (1) record the transmission input speeds and rotation directions for input shaft 1 and 2. They are designed as an assembly made up of two individual speed sensors in one housing. The pickup or sensor wheel (2) records the speed of input shaft 1, while the fixed gear wheel for 2nd gear records the speed of input shaft 2. A coded PWM signal is generated as the output signal.
The supply voltage for the speed sensors is 8.5 V.
The diagnostic system checks the sensor as follows:
- Short circuit to ground
- Short circuit to supply voltage
- Open circuit in line
- Signal plausibility
Pressure sensors
The two pressure sensors (1) for measuring the clutch pressure values of the two Doppelkupplung clutches are read directly at the rotary transmission feed-through point.
They are fitted in the centering plate and are connected to the wire harness (3) by connectors (2). The supply voltage is 5 V.
The diagnostic system checks the sensor as follows:
- Short circuit to ground
- Short circuit to supply voltage
- Open circuit in line
- Signal plausibility
Temperature sensor
The temperature sensor is used to record the sump temperature of the hydraulic oil. This involves measuring a temperature-dependent resistance.
The supply voltage is 5 V.
The diagnostic system checks the sensor as follows:
- Short circuit to ground
- Short circuit to supply voltage
- Open circuit in line
- Signal plausibility