Computer / Electronic Control Unit
An electronic control unit (ECU) is a device responsible for regulating operations of electronic systems of a car. In essence, computer control units are simple computers that receive input parameters and provide output parameters.
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The electronic control unit receives signals from sensors and provides output signals to electronic transmission components. ECU does not only receive signals from the sensors but also the engine control unit for optimal operation. ECU determines the ideal time for sensors to change gears.
Transmission control unit / module is an ECU that controls all the functions of the transmission system. An array of sensor read the various factors such as engine temperature, vehicle speed and engine speed that control gear shifting. They relay this information to the transmission control unit.
Transmission control unit decides how transmission will behave according to the information from the vehicle. The transmission control module is a computer that helps the automatic transmission chooses a suitable gear at a particular time. This helps to achieve optimal levels of fuel economy and driving performance. It is a pivotal component of an automatic transmission system.
The inputs depend on the design of the transmission. However common inputs include:
- Vehicle speed sensors
- Throttle positions sensors
- Fluid pressure sensors
- Wheel speed sensors
- Brake light sensors
These sensors work in hand with transmission to lock torque converter, monitor the speed of the vehicle and change gears. In most automobiles, TCU works with in conjunction with on board computer of the vehicle to adjust fuel flow, engine timing and other critical functions of the vehicle. The sensors are mounted on the wheels, transmission output shaft and engine crankshaft. Many vehicles also use a transmission control unit as a safety device.
Similarly, output signals vary depending on the transmission design. Some common components that receive signals from the transmission control unit include:
- Engine control unit
- Shift solenoids
- Torque convert clutch
- Shift lock
- Pressure control solenoid
Sign of Faulty transmission system
Illuminating engine warning light
Engine warning light could indicate several problems. However, if the check engine light and shift problems occur concurrently, your vehicle’s transmission control unit may be having a problem.
Automatic transmission depends on the automatic control unit to shift gears. A bad TCU will result in unpredictable shifting. This is not only irritating but can also cause an accident.
Problem Downshifting or changing to a higher gear
Your transmission should shift into higher gears as you gradually increase speed. If a faulty TCU fails to shift to a higher gear, it will be very hard to attain your intended speed.
Similarly, you could experience the opposite if the above situation. If your TCU is faulty, you may be in high gear as you come to a halt. When you ready to move again, your car may be in high gear which is unsuitable for acceleration. As a result, you may not be able to move at all.
Other signs including delayed shifting, lousy fuel economy and sticking in the same gear. Once you notice these problems do not hesitate to contact the technician.
The transmission control unit is a crucial component in the transmission system. You should ensure it is always in good shape.
Learn more about your vehicle’s transmission: