Transmission Control Module

WARNING: This page is about a different variant/trim than selected.

The Transmission Control Module (TCM) outputs signals to control the hydraulic operation of the transmission. Signals are sent to the shift control solenoid valves and the Electronic Pressure Regulating Valve's (EPRS).

The TCM processes signals from the transmission speed and temperature sensors, the Transmission Control Switch (TCS), the Powertrain Control Module (PCM) and other vehicle systems. From the received signal inputs and pre-programmed data, the TCM calculates the:

Correct gear
Torque converter clutch setting
Optimum pressure settings for gear shift and lock-up clutch control.

The PCM supplies the engine management data over the FlexRay systems bus. The TCM requires engine data to efficiently control the transmission operation, for example:

Flywheel torque
Engine speed
Accelerator pedal angle
Engine temperature.

The steering angle sensor and the Anti-lock Brake System (ABS) control module also supply data to the TCM on the FlexRay systems bus. The TCM uses data from these systems to suspend gear changes when the vehicle is cornering and/or the ABS control module is controlling braking or traction control.

The Body Control Module/Gateway Module (BCM/GWM) supplies steering wheel paddle data over the FlexRay systems 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
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. This allows precise control the hydraulics of the automatic transmission. In addition, the amount and duration of engine interventions are supplied to the engine management via the FlexRay systems bus.

The TCM determines the position of the TCS using signals from the TCS via the High Speed (HS) Controller Area Network (CAN) systems bus.

The TCM transmits the position of the TCS and any manual gear selected on the FlexRay systems bus to the BCM/GWM. This information is shown in the gear selector display in the instrument cluster.

Engine Stall

If the engine stalls it will coast down in gear, with the transmission providing drive to the engine. A restart can be attempted at this point and the engine may start and the driver can continue.

If the coast down speed reduces such that the speed of the engine is less than 100 Revolutions Per Minute (RPM), the transmission will go to neutral, D illumination will flash in the instrument cluster. The driver needs to select neutral or park and then press the brake pedal to restart the engine.

If the start/stop switch is pressed when driving, the message ENGINE STOP BUTTON PRESSED is displayed in the message center but there will be no change to the ignition state. If the driver requires to switch off the engine, the start/stop switch must be pressed for a second time. The engine will be stopped and will be back driven by the transmission as the vehicle coasts down.