Control Module: Description and Operation

Economy, Sport and Manual Modes

The Automatic Transmission Control Module has various different driving modes available, with Economy being selected automatically on start up. When the vehicle is in High range, Sport mode can be selected. This will make the gear change much more sensitive to throttle movement, thereby shifting down earlier and holding onto lower gears longer than the Economy mode equivalent. If the vehicle is in Low range, then Manual mode can be selected. This will make the gear box change into the selected gear as quickly as possible and hold on to that gear at all speeds, i.e. if "3" is selected, then the gear box will not shift down to "2" or "1" as the vehicle slows down. It will only change gear to prevent the vehicle from stalling.

Interface to Engine Control Module

The Automatic Transmission Control Module takes the engine torque, engine speed and throttle angle signals from the ECM, calculates which gear is required, outputs to the solenoid valves and sends a torque reduction signal back to the ECM, thereby retarding the ignition point on each of the cylinders and so giving a reduction in engine power during gear changes that result in a smooth change.

The engine torque is received by the Automatic Transmission Control Module on its pin 21, the engine speed on pin 3 and the throttle angle on pin 47. The torque reduction signal is sent to the ECM from the Automatic Transmission Control Module via its pin 32.