Pressure Control Solenoid

Fig 1: View Of Pressure Control Solenoid

Courtesy of GENERAL MOTORS CORP.

The pressure control (PC) solenoid is a precision electronic pressure regulator that controls transaxle line pressure. This control is based on flow of current through solenoid coil windings. As the flow of current is increased, the magnetic field which is produced by the coil moves the solenoid's plunger further away from the exhaust port. Opening the exhaust port decreases output fluid pressure regulated by the PC solenoid, which ultimately decreases line pressure.

The powertrain control module (PCM) or transaxle control module (TCM) controls the PC solenoid based on various inputs, including throttle position, transaxle fluid temperature, MAP, and gear state.

The PCM/TCM controls the PC solenoid on a positive duty cycle at a fixed frequency of 614 Hz. Duty cycle is defined as percent of time current is flowing through the solenoid coil during each cycle. A higher duty cycle provides a greater current flow through the solenoid. The high (positive) side of the PC solenoid electrical circuit at the PCM/TCM controls PC solenoid operation. The PCM/TCM provides a ground path. The PCM/TCM monitors average current and continuously varies the PC solenoid duty cycle to maintain the correct average current flow.

The resistance of the PC solenoid should measure between 3-5 ohms at 20°C (68°F).