Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
System Overview: Notes
AW55-50 (and AW50AWD) is a 5-speed electronically controlled automatic transmission with a lock-up function for the three highest gears. The transmission control module (TCM) adapts the gear changes to ensure that the correct gear is selected for the driving mode, engine load, driver requirements, speed etc. This gives good fuel economy combined with increased comfort by ensuring smoother gear changes and lower noise levels.
The transmission control module (TCM) receives information about the desired gear position and driving mode from the driver. In conjunction with the signals from a number of sensors in the transmission and the engine control system, unlike with a purely hydraulically controlled transmission, this allows the control module to calculate the optimal shifting points and engagement of lock-up. The control module allows for small changes in the operating conditions and adapts the various transmission functions to ensure that the correct gear is always selected in relation to the driving mode selected by the driver.
This adaptability guarantees smooth and consistent gear shift quality throughout the operational life of the transmission.
In order to precisely determine the gear shift and lock-up engagement points based on the driving mode selected, the control module receives and processes information about the following:
- Selected gear position - from the gear-shift position sensor
- Selected driving mode economy/sport - reactive function programmed in the control module which is controlled by the speed at which the accelerator pedal (AP) is depressed. Quick "pedal movement" = sport mode. Winter (W) mode is activated using a switch on the gear selector assembly
- Vehicle speed - from the brake control system via the Controller area network (CAN)
- Transmission input shaft rpm - from the transmission speed sensor
- The transmission output shaft rpm - from the transmission output speed sensor
- The engine speed (RPM) and torque and throttle opening - from the engine management system via the Controller area network (CAN)
- If the brake pedal is depressed and to what extent - from the brake control system via the Controller area network (CAN)
- If the accelerator pedal (AP) is depressed and to what extent - from the engine management system via the Controller area network (CAN)
- Transmission fluid temperature - from the temperature sensor in the transmission
- Engine coolant temperature - from the engine control module (ECM) via the Control area network (CAN).
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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