Electronic Shift Control System

GEAR SHIFT CONTROL SYSTEM





Transmission Control Module (TCM)








The Powertrain (Engine) Control Module (PCM) controls the shift solenoid-B (2nd brake solenoid valve) and the shift solenoid-A (direct clutch solenoid valve) by sending electric signals to them so as to attain automatic gear shift between the 1st and 2nd gears, and the 2nd and 3rd gears. Equipped as PCM sensed parameters are the throttle position sensor, transmission range switch (sensor) and Vehicle Speed Sensor (VSS). These switch and sensors sense the throttle valve opening, selector lever's position and vehicle speed, and send those signals to the PCM. Then, the PCM opens and closes valves of the above solenoids according to these signals.


Throttle Position Sensor (TP Sensor)




The Throttle Position (TP) sensor consisting of a potentiometer is connected to the throttle valve shaft. Throttle valve opening signal (output voltage) is transmitted from throttle position sensor to the Powertrain (Engine) Control Module (PCM) as voltage signal. PCM uses it as one of the signals to control transmission gear shift.


Transmission Range Switch




Being linked with the selector lever, this switch changes selector lever positions into electric signals and send them to the Powertrain (Engine) Control Module (PCM). The contact points of this switch for P and N ranges are also connected with the starting motor circuit. So when the selector lever is shifted to the P or N position, the contact points for P or N range are connected and cause the starting motor to operate by turning the starter switch ON. When the selector lever is in any other position than P and N, the switch remains OFF and therefore the starting motor cannot be operated, that is, the engine cannot be started. Also, as its contact point for R range is connected with the back up light circuit, only when the selector lever is shifted to R range, the contact point contacts to light the back up light.

Shift Solenoid-a And Shift Solenoid-b (direct Clutch And 2nd Brake Solenoid Valves)



These solenoid valves are mounted on the valve body. They are turned ON (valve is open) and OFF (valve is closed) by the signals from the Powertrain Control Module (PCM) and actuate each shift valve (1-2 and 2-3 valves) so as to control transmission gear shift. Shift solenoid-B (2nd brake solenoid valve) operates 1-2 shift valve, and shift solenoid-A (direct clutch solenoid valve) does 2-3 shift valve.


Operation Of Shift Solenoid-a And Shift Solenoid-b (direct Clutch And 2nd Brake Solenoids)





Vehicle Speed Sensor



The Vehicle Speed Sensor (VSS) consists of a magnetic core with magnet and coil. It is mounted on transmission case with 0.6 mm (0.024 inch) air gap between the core end and countershaft gear tooth. While the countershaft rotates, magnetic flux is cut by gear tooth thus a pulse is generated in the sensor coil according to the speed. And then, the pulse is transmitted to Powertrain (Engine) Control Module (PCM) as speed signal.


AUTOMATIC SHIFT DIAGRAM



Automatic shift schedule as a result of shift control is shown. In case that selector lever is shifted to L at a higher than 58 km/h (36 mile/h) speed, 2nd gear is operated and then down shifts to 1st at a speed lower than that. No up shift is available in L.