Electronic Transmission

On most vehicles, PCM controls transmission and other vehicle functions. PCM monitors a number of engine/vehicle functions and uses data to control shift solenoid "A", shift solenoid "B", TCC solenoid and the force motor. PCM also regulates TCC engagement, upshift pattern, downshift pattern and line pressure (shift quality).

• Shift Solenoid "A" (1st-2nd)
  
  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. The solenoids work in four on/off combinations to shift the transmission into different gears. When on, solenoid redirects fluid to act on the shift valves.
• Shift Solenoid "B" (2nd-3rd)
  
  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. The solenoids work in four on/off combinations to shift the transmission into different gears. When on, solenoid redirects fluid to act on the shift valves.
• Transmission Pressure Control Solenoid
  
  The transmission pressure control solenoid is an electronic pressure regulator that controls pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve. The PCM controls the pressure control solenoid by commanding current of 0.1-1.1 amps. This changes the duty cycle of the solenoid, which can range 5-95 percent (typically less than 60 percent). High amperage (1.1 amps) corresponds to minimum line pressure, and low amperage (0.1 amp) corresponds to maximum line pressure (if the solenoid loses power, the transmission defaults to maximum line pressure). The PCM commands the line pressure values, using inputs such as engine speed and TP sensor voltage. The pressure control solenoid takes the place of the throttle valve or the vacuum modulator that was used on past model transmissions.