Solenoid testing machines are used for checking the state of solenoids produced by different manufacturers of automatic transmissions. Separate solenoid test blocks make it possible to run tests for the majority of most popular makes on the actual international market. Modern Solenoid Test machines now typically come as a universal model and allow to cover any transmission specialists’ preferences in transmission rebuilding operations. Modern Solenoid Test tools allow possibility to run tests at maximally high required temperature and solenoids are tested as they function with the valve body, as originally designed. The automatic transmission solenoid is an electromechanical regulator in the gearbox, in response to the computer impulse it opens or closes the channel in the hydraulic unit to control flows of hydraulic fluid. Solenoids control the hydraulic switching of operation modes in modern automatic transmissions, CVT and DSG. The solenoid is inserted in the channel of the hydraulic unit and is fixed by bolts (or a pressure plate) and at the other end through the plug of the wiring harness it is connected to the electronic control unit of the automatic transmission.