Electronic Transmission

The transaxle/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 1-2, 3-4 and 2-3 shift solenoids, TCC and, on some models, pressure control solenoid to regulate TCC engagement, upshift pattern, downshift pattern and line pressure (shift quality).

• 1-2, 3-4 Shift Solenoid
  
  1-2, 3-4 shift solenoid is attached to valve body and is a normally open exhaust valve. PCM activates solenoid by grounding it through an internal quad-driver. The 1-2, 3-4 solenoid 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.
• 2-3 Shift Solenoid
  
  2-3 shift solenoid is attached to valve body and is a normally open exhaust valve. PCM activates solenoid by grounding it through an internal quad-driver. The 2-3 solenoid is off in 3rd and 4th gears but on in 1st and 2nd gears. When on, solenoid redirects fluid to act on the shift valves.
• Pressure Control Solenoid
  
  Pressure Control (PC) solenoid is attached to the valve body and controls line pressure by moving a pressure regulator valve against spring pressure. PCM varies line pressure based upon engine load. Engine load is calculated from several inputs including Manifold Absolute Pressure (MAP) sensor, Transmission Fluid Temperature (TFT) sensor, TP sensor and gear position. Line pressure is actually varied by changing the amperage applied to pressure control solenoid from .02 (maximum pressure) to 1.1 amps (minimum pressure). The PCM continuously varies the PC solenoid valve amps to maintain the correct average current flowing through the valve.