Theory Of Operation

WARNING: This page is about a different car, the 2015 Jeep Renegade. However, it is still accessible from the selected car via links, so may be relevant.

This diagnostic checks for an over-temperature condition of the hydraulic Electro-Pump (EP). For example, a fluid leak or excessive gear shifting (excessive frequency of gear-shifts requested by the driver) may cause this condition. The TCM performs an over-temperature diagnosis based on the internal pump temperature (rotor and brushes) estimated by the pump thermal model. Specific recovery actions may be activated to prevent the pump from overheating. The diagnostic monitoring is based on three levels of severity and recovery by comparing the EP estimated brush temperature to three different thresholds: Temp 1 is a dynamic threshold and it is a function of pump duty cycle. Temp 2 is a dynamic threshold and it is a function of pump duty cycle and excessive gear shifting. Temp 3 is a fixed threshold and it is equal to the maximum calculated pump temperature.

Specific recovery actions are as follows:

If Temp 1 (Pump Overheating) is detected the TCM will take the follow actions: Neutral is engaged after a short timeout during standstill, the EP duty cycle is reduced, the odd and even clutch actuators dither is reduced and the odd clutch self tuning is disabled.

If Temp 2 (Pump Critical Temperature) is detected the TCM will take the follow actions: Neutral is engaged after a short timeout during standstill, the EP duty cycle is reduced, the odd and even clutch actuators dither is reduced, the odd clutch self tuning is disabled, the transmission is forced to operate in full automatic mode, gear shifts are minimized and the gear shift requests by the driver are ignored.

If Temp 3 (Pump Max Temperature) is detected the TCM will take the follow actions: The pump is switched off, Neutral is engaged after a short timeout during standstill, the transmission limp home is activated so that up shifts are limited to a maximum gear, the engine limp home is activated so that engine speed is limited to a maximum value, the transmission is forced to operate in full automatic mode using even gears only and creeping is disabled.