Transmission fluid temperature sensor: Notes

The transmission fluid temperature sensor is mounted in the gear case and provides the control module with information on the current transmission fluid temperature. The sensor is of NTC type.

The control module senses the transmission fluid temperature by supplying the sensor with +5 V current through a 1 kohm resistor (built into the control module) and out on pin 6.

The sensor is grounded at grounding point G41S.

The control module uses the fluid temperature for the following purposes:

Fig 1: Identifying Transmission Fluid Temperature Sensor Communication Flow

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Transmission Fluid Temperature Sensor Connection Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

At fluid temperatures below 0°C, no Lock-up takes place.
At a fluid temperature of approx. 170°C, the TCM sends the bus information "HIGH TRANSMISSION FLUID TEMP ON" and the corresponding message is then displayed on the SID.
When the fluid temperature drops to below 140°C, the information "HIGH FLUID TEMP AUTO TRANSMISSION OFF" is sent on the bus. The SID message then goes out and operation of the transmission returns to normal.
At fluid temperatures below 0°C, system pressure is increased by 3.3 bar for 5 seconds when N-D or N-R shifts are performed.
At fluid temperatures 0-20°C the same function is implemented but the increase in pressure is reduced linearly from 3.3 bar (at 0°C) to 0 bar (at 20°C).
The transmission fluid temperature is above 150 °C.