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Solenoid valve ST, for system pressure

Solenoid valve ST, for system pressure



Solenoid valve ST is located in the valve housing which is mounted on the transmission casing. The solenoid regulates the automatic transmission's system pressure.

The solenoid is not grounded to the gearbox but internally in the control module. It is supplied via control module pin 16 with feed back to control module pin 34. The solenoid is controlled by a varying current from the control module, where the current is affected primarily by the throttle position. A high current, approx. 1 A, causes low fluid pressure and when the current is low or if it is cut, the system pressure will be at maximum.

When shifting from N to R, the control module lowers the system pressure to avoid jerky shifting. When the oil temperature is greater than 10°C, and the vehicle speed is greater than 5 km/h, the control module increases the system pressure to reduce the gear-shifting times.

The function is disengaged in the following situations: • fluid temperature higher than 20°C • vehicle speed greater than 7 km/h • change in position of selector lever

The coil resistance in the solenoid is approx. 4 ohms.

The current strength at idling speed with the handbrake applied and the selector lever in position D is approx. 900 mA and the fluid pressure 3.4-4.6 bar.

Electrical faults (short-circuit to ground or B+ and open circuits) in the solenoid valve or wiring harness will put the transmission in limp-home mode.