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Transmission control unit (TCM) or Engine control unit (ECM)..

A transmission control unit or TCU is a device that controls modern electronic automatic transmissions. A TCU generally uses sensors from the vehicle as well as data provided by the Engine Control Unit (ECU) to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.

Most TCU are not part of the transmission, GotTransmissions.com advises potential customers to have the transmission scanned before transmission removal, (if you have a transmission failure or functional problems), in order to determine if that was the problem.

Electronic automatic transmissions have been shifting from  hydro-mechanical controls to pure electronic controls since the late 1980’s. Since then, development has been interactive and todays designs exist from several stages of electronic automatic transmission control development. Transmission solenoids are a key component to these control units.

The evolution of the modern automatic transmission from the hydroelectric controls and the integration of pure electronic controls have allowed great progress in recent years. The new era automatic transmission is now able to achieve better fuel economy, reduced engine emissions, greater shift reliability, improved shift quality, advanced shift speeds and improved vehicle driveability. The  range of programability depends on the vehicle and it’s purpose. Made possible by a TCU (transmission control unit) that allows the modern automatic transmission to be used with appropriate transmission behavior for each application.

Simply put, the TCM receives input from a variety of devices such as the VSS, TPS, MLPS, Brake switch and more depending on the vehicle. Obviously if you do experience a transmission problem or failure it is wise to use a scan tool on the inputs as well.

GotTransmissions.com blog will provide realistic information on the inputs and how they work in order to make better use of this post.

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