Transmission Control Module (TCM)

The TCM outputs signals to control the shift control solenoid valves and the EPRS (Electronic Pressure Regulating Solenoid)'s to control the hydraulic operation of the transmission.

The TCM processes signals from the transmission speed and temperature sensors, the TCS, the ECM and other vehicle systems. From the received signal inputs and pre-programmed data, the TCM calculates the correct gear, torque converter clutch setting and optimum pressure settings for gear shift and lock-up clutch control.

The ECM supplies the engine management data over the HS CAN Powertrain bus. The TCM requires engine data to efficiently control the transmission operation, for example; flywheel torque, engine speed, accelerator pedal position, engine coolant temperature. The ABS (Anti-lock Brake System) control module also supplies data to the TCM on the HS CAN Powertrain bus. The ABS control module receives the steering angle data from the SASM (Steering Angle Sensor Module) via the HS CAN Chassis bus, converts the message and forward it to the TCM via the HS CAN Powertrain bus. The TCM uses data from these systems to suspend gear changes when the vehicle is cornering and/or the ABS is controlling braking or traction control.

The CJB (Central Junction Box) supplies steering wheel paddle data over the HS CAN Powertrain bus. The TCM uses this to schedule driver requested upshifts and downshifts.

Using the signal inputs and the memorized data, the TCM control program computes the correct gear and torque converter lock-up clutch setting and the optimum pressure settings for gear shift and lock-up clutch control. Special output-side modules (power output stages, current regulator circuits), allow the TCM to control the solenoid valves and pressure regulators and consequently precisely control the hydraulics of the automatic transmission. In addition, the amount and duration of engine interventions are supplied to the engine management by way of the HS CAN Powertrain bus.

The TCM determines the position of the TCS using signals from the TCS on the HS CAN Powertrain bus and a hardwired connection for the 'P' (park) position determination.

The TCM transmits the position of the TCS and any manual gear selected on the HS CAN Powertrain bus. This information is shown in the transmission status display in the IC.