Electronic Component Description: Solenoids
The control valve body contains both normally closed and normally open solenoids. A normally closed solenoid remains closed until a signal from the TCM energizes the solenoid. A normally open solenoid remains open until the TCM energizes the solenoid. When a solenoid valve is in the closed position, the valve blocks the flow. When a solenoid valve is in the open position, flow is permitted through the valve. The pulse width modulated solenoid "F" (1) and the ON/OFF shift valve solenoids "C", "D", and "E" ((4), (2) and (3) respectively) are normally closed. Both solenoid types have an orifice, electrical windings, an iron core, and a steel check ball. See Fig 1.
The solenoids used differ in their ability to control flow or fluid pressure. The solenoids may operate in the open or closed state with no modulation capability (solenoids "C", "D", and "E"), an intermediate flow and resultant pressure based on duty cycle (solenoid "F") or produce pressure proportional to current (solenoids "A" and "B").
Shift solenoids "C", "D", and "E" provide the necessary logic to distribute fluid to the correct clutches. The shift solenoids provide either full control main pressure or exhaust to the head of each of the corresponding shift valves "C", "D", and "E". Since the valve states (stroked or unstroked) are critical to providing the correct transmission gear range, each shift valve has a pressure switch (located in the pressure switch manifold) which provides feedback to the computer as to the valve's position.
Trim solenoids "A" and "B" ((6) and (5), respectively) are used to control oncoming, off-going, and holding pressure to the five clutches. These solenoids are referred to as Pressure Proportional to Current (PPC) solenoids, since the output hydraulic pressure supplied by these solenoids is proportional to the controlled current command.