ELECTRONIC CONTROL SYSTEM The electronic control system, which controls the shift points and the operation of the lock–up clutch, is composed of the following three parts: 1. Sensors These sensors sense the vehicle speed, throttle opening and other conditions and send this data to the ECM in the form of electrical signals. 2. ECM The ECM determines the shift and lock–up timing based upon the signals from sensors, and controls the solenoid valves of the hydraulic control unit accordingly. 3. Actuators These are three solenoid valves that control hydraulic pressure acting on the hydraulic valves to control shifting and lock–up timing. SENSORS DRIVING PATTERN SELECTOR PARK/NEUTRAL POSITIOIN SWITCH THROTTLE POSITIOIN SENSOR VEHICLE SPEED SENSOR STOP LIGHT SWITCH O/D MAIN SWITCH CRUISE CONTROL ECU ENGINE COOLANT TEM-PERATURE SENSOR A/T FLUID TEMPERATURE SENSOR ECM Control of shift timing Control of lock–up timing Self–diagnostic system Back–up system ACTUATORS NO. 1 SOLENOID VALVE NO. 2 SOLENOID VALVE LOCK–UP SOLENOID VALVE O/D OFF INDICA-TOR LIGHT