Sensors (page 4 of 5)

AUTOMATIC GEARBOX - JATCO

DESCRIPTION AND OPERATION

44-25

Fluid Temperature Sensor

The fluid temperature sensor is located within the gearbox on the valve block. The EAT ECU uses this sensor to 
monitor the gearbox fluid temperature.

When the fluid is cold, the EAT ECU changes gear at higher engine speeds to promote faster fluid warm-up. If the 
fluid temperature becomes too high, the EAT ECU transmits a cooling request on the CAN link to the ECM to operate 
the cooling fans.

The fluid temperature sensor has an electrical output to pin 39 of the EAT ECU which also provides an earth path for 
the sensor.

The fluid temperature sensor is a negative temperature coefficient sensor. As the temperature rises, the resistance 
in the sensor decreases. As temperature decreases, the resistance in the sensor increases and the output voltage to 
the EAT ECU changes in proportion.

The output voltage from the sensor is in the range of 0 - 2.5 Volts with the lower voltage representing the highest 
temperature.

The change in resistance is proportional to the temperature of the gearbox fluid. From the resistance of the sensor, 
the EAT ECU calculates the temperature of the gearbox fluid. Should the fluid temperature sensor fail the EAT ECU 
uses the last recorded EAT ECU value as a default value.

Fluid Temperature Sensor Resistance Values

Temperature 

°

C (

°

F)

Resistance k

Ω

-40 (-40)

54.90

-20 (-4)

16.70

0 (32)

6.02

20 (68)

2.50

40 (104)

1.16

60 (140)

0.59

80 (176)

0.33

100 (212)

0.19

120 (248)

0.12

140 (284)

0.08