RAM 2500 Truck 2WD V8-5.9L VIN 5 HDC (1998)
Transmission Temperature Sensor/Switch: Description and Operation
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 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 Powertrain Control Module (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.
