Grand Cherokee 2WD L6-4.0L VIN S (1997)
Transmission Temperature Sensor/Switch: Description and Operation
Transmission Temperature Sensor - PCM Input
TRANSMISSION TEMPERATURE SENSOR-PCM INPUT
This input is used in the shift operation for 4-speed electronic transmissions only. The temperature data is used for: torque converter clutch
operation, overdrive shift, low temperature shift compensation, wide open throttle shift strategy and governor pressure transducer calibration.
Transmission fluid temperature readings are supplied to the transmission control module by the thermistor. The temperature readings are used to
control engagement of the fourth gear overdrive clutch, the converter clutch, and governor pressure. Normal resistance value for the thermistor at
room temperature is approximately 1000 ohms.
The Powertrain Control Module (PCM) prevents engagement of the converter clutch and overdrive clutch, when fluid temperature is below
approximately 10 °C (50 °F).
If fluid temperature exceeds 126 °C (260 °F), the PCM causes a 4-3 downshift and engage the converter clutch. Engagement is according to the
third gear converter clutch engagement schedule.
The overdrive OFF lamp in the instrument panel illuminates when the shift back to third occurs. The transmission will not allow fourth gear
operation until fluid temperature decreases to approximately 110 °C (230 °F).
The thermistor is part of the governor pressure sensor assembly and is immersed in transmission fluid at all times.
