• ECT Aside from having an ECU which controls shifting based upon electrical speed and throttle opening signals, the ECT is basically the same as a fully hydraulic controlled automatic transmission. The ECT controls shifting in the following manner: [DIAGRAM showing system with Throttle Position Sensor, Torque Converter, Planetary Gear Unit, Hydraulic Control Unit (containing Shift Valves and Solenoid Valves), Vehicle Speed Sensor, and ECU connected by signal lines] Vehicle Speed Sensor Planetary Gear Unit Hydraulic Control Unit Shift Valves Solenoid Valves Throttle Position Sensor ECU (Throttle Opening Signal) (Vehicle Speed Signal) AT3255 THROTTLE POSITION SENSOR The throttle opening is sensed by the throttle position sensor, which sends this data to the ECU in the form of electrical signals. VEHICLE SPEED SENSOR The vehicle speed is sensed by the vehicle speed sensor, which sends this data to the ECU in the form of electrical signals. ECU The ECU determines the shift timing on the basis of the vehicle speed and throttle opening signals, and operates the solenoid valves in the hydraulic control unit to control the fluid flow and movement of the shift valves. These valves in turn control the fluid passage to the clutches and brakes in the planetary gear unit, which control the shifting of the transmission.