Electronic Transmission (4L80-E)

On gasoline vehicles equipped with 4L80-E transmission, Powertrain Control Module (PCM) controls transmission and other vehicle functions. On diesel vehicles, Transmission Control Module (TCM) controls electronic transmission, but no other components. PCM/TCM monitors a number of engine/vehicle functions and uses data to control shift solenoid "A", shift solenoid "B", TCC and the force motor and 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/TCM 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. When on, solenoid redirects fluid to act on the shift valves. Solenoid "A" is Blue. Code 82 is associated with solenoid "A".
• Shift Solenoid "B"  Shift solenoid "B" is attached to the valve body and is a normally open exhaust valve. PCM/TCM 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. When on, solenoid redirects fluid to act on the shift valves. Solenoid "B" is Red. Codes 81, 86 and 87 are associated with solenoid "B".
• 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 replaces the throttle valve or vacuum modulator used on past transmissions. PCM/TCM varies line pressure based upon engine load. Engine load is calculated from various inputs, especially the TPS. 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 fluid contamination from causing pressure regulator valve to stick.