Description

These transmissions have unique shift schedules depending on the temperature of the transmission oil. The shift schedule is modified to extend the life of the transmission while operating under extreme conditions.

The oil temperature is now measured on all 96 and newer 42LE transmissions. A thermistor is installed in the Manual Valve Lever Position Sensor (MVLPS) (42LE).

On all 93-95 MY 42LE, and 96 MY with code 74 present, the transmission oil temperature is calculated through a complex heat transfer equation which uses engine coolant temperature, battery/ambient temperature, and engine off time from BCM.

These inputs are received from the CCD bus periodically and used to initialize the oil temperature at start up.

Once the engine is started, the TCM updates the transmission oil temperature based on torque converter slip speed, vehicle speed, gear, and engine coolant temperature to determine an estimated oil temperature during vehicle operation.

Vehicles with "calculated oil temperature" track oil temperature reasonably accurately during normal operation. However, if a transmission oil cooler is added, a transmission is overfilled, a transmission oil cooler becomes restricted, or if a customer drives aggressively in low gear the calculated oil temperature will be inaccurate. Consequently the shift schedule selected may be inappropriate for the current conditions.