Electronic Transmission

On vehicles equipped with electronic transmission, transmission is controlled by the Powertrain Control Module (PCM). PCM controls other vehicle functions as well as the transmission. The PCM monitors a number of engine/vehicle functions and uses the data to control shift solenoid "A", shift solenoid "B", TCC and the force motor to regulate TCC engagement, upshift pattern, downshift pattern and line pressure (shift quality).

• Shift Solenoid "A"

Shift solenoid "A" is attached to the valve body and is a normally open exhaust valve. PCM activates solenoid by grounding it through an internal quad-driver. Solenoid "A" is on in 1st and 4th gears but off in 2nd and 3rd gears. When on, solenoid redirects fluid to act on the shift valves.

• Shift Solenoid "B"

Shift solenoid "B" is attached to the valve body and is a normally open exhaust valve. PCM activates solenoid by grounding it through an internal quad-driver. Solenoid "B" is on in 3rd and 4th gears but off in 1st and 2nd gears. When on, solenoid redirects fluid to act on the shift valves.

• Force Motor

Force motor is attached to the valve body and controls line pressure by moving a pressure regulator valve against spring pressure. Force motor takes the place of the throttle valve or vacuum modulator used on past model transmissions. PCM varies line pressure based upon engine load. Engine load is calculated from various inputs, especially the TP sensor.

• Line pressure is actually varied by changing the amperage applied to the force motor from zero (high pressure) to 1.1 amps (low pressure). The force motor is periodically pulsed to prevent the pressure regulator valve from sticking due to fluid contamination.