General and components: General
The AW 50-42 is an electronically-controlled four speed automatic transmission with torque converter lock-up of the three highest gears. Because the transmission is controlled by an electronic control module, gear-shifting can be controlled to allow the correct gear to be selected for driving conditions, engine load, driver's wishes, speed, etc. This gives good fuel economy combined with top-class performance and increased comfort by ensuring smoother gearshifting and lower noise levels.
A control module receives information about the selected gear and driving mode setting. This, together with signals from a number of sensors providing information about the running conditions of the car, is processed by the control module. The control module calculates the optimum gear shifting and lock-up engagement points, depending on the driving mode selected. The control module then controls gearshifting and lock-up engagement by acting on the transmission hydraulic system. The control module also affects the quality of gearshifting by adjusting hydraulic line pressure at the instant of gear shifting.
The transmission's electronic control system receives continuous information from a number of sensors, as well as from the engine management system. Unlike transmissions with exclusively hydraulic control systems, the control system can adapt to extremely small changes in operating conditions. It can control the different transmission functions so that the correct gear for the driving mode selected by the driver, is always selected.
To facilitate fault-tracing, the control module has a built-in on-board diagnostic system (OBD II system) which records any faults in the control system and transmission. These faults can be read off via the data link connector (DLC).