Torque Converter: Description and Operation

OPERATION
The Transmission Control Module (TCM) is able to monitor the state of the torque converter clutch at all times. There are three operating modes for the converter, as follows:
1. Fully open - Torque converter 'unlocked'
2. Fully closed - Torque converter 'locked'
3. Slip control - The TCM monitors slip and may apply sufficient pressure to allow a small degree of slip. This mode maximizes economy by reducing slip to a minimum whilst providing isolation from drive-line shunt and vibration.

MONITORING PROCEDURE
The TCM constantly measures the slip within the torque converter by comparing engine speed via Controlled Area Network (CAN) and input (turbine speed). Differences in these speeds indicate the amount of slip.

PRESSURE REGULATION
The TCM supplies an internally switched + 12V to the #4 pressure regulator via pins EM007/052 and EM007/053. The regulator is operated by switching the other side to ground via pin EM007/004. Pressure is controlled by the time, i.e. the duty cycle, that the pressure regulator is switched on; this is 'Pulse Width Modulation' (PWM).

CIRCUIT DIAGRAM, PRESSURE REGULATORS
Please see DTC P0702 for associated pressure regulator circuit. Refer to Automatic Transmission, Testing and Inspection.