Transmission fluid temperature sensor
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Transmission fluid temperature sensor
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The transmission fluid temperature sensor is mounted in the gearcase 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:
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At fluid temperatures below 0°C, no Lock-up takes place.
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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 AUT TRANSMISSION OFF” is sent on the bus. The SID message then goes out and operation of the transmission returns to normal.
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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).
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The transmission fluid temperature is above 150 °C.
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Diagnostics
In the event of a fault in the temperature sensor, three different diagnostic trouble codes may be generated:
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If the temperature increases or decreases too slowly during the first 15 minutes of driving, diagnostic trouble code P0711 will be generated.
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In the event of short to B-, diagnostic trouble code P0712 will be generated.
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In the event of short to B+ or an open circuit, diagnostic trouble code P0713 will be generated.
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If the temperature rises to 150°C, Lock-Up will be engaged in 2nd gear. Engaging Lock-Up prevents slip in the torque converter, which makes the temperature drop. The shifting points are altered as well, which means upshifts occur at higher engine speeds and downshifts at lower engine speeds in the normal program.
If the temperature rises to 157°C, the engine torque is reduced to 200 Nm.
The adaptive shifting program is deselected when:
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the WINTER program is selected.
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The ignition key is turned to the ON or OFF positions.
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The load decreases so much that an adaptive shifting pattern no longer is needed.
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CHECK GEARBOX lamp lights up.
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