LS430 − NEW FEATURES 23 Orifice Switching Control At extremely low temperatures, the ATF becomes thick, making the oil pump susceptible to drawing air. For this reason, the orifice switching control reduces the volume of the oil in the transmission and increases the volume of oil drawn by the oil pump, in order to prevent the oil pump from drawing air. While stopped in 1st, the ECM turns OFF the solenoid valve S1 and turns ON the solenoid valve S4 in order to apply the line pressure to the 1-2 shift valve and the SL1 relay valve.
The 1-2 shift valve and the SL1 relay valve close the oil passage for the secondary pressure from the secondary regulator valve, thus causing the secondary pressure to pass through orifice “A”. As a result, the volume of oil in the transmission decreases. While stopped in a gear other than 1st, the secondary pressure from the secondary regulator valve travels through either or both of the 1-2 shift valve and SL1 relay valve, and passes through orifice “B”, in order to lubricate the inside of the transmission. As a result, the volume of the oil in the transmission does not decrease.
Solenoid Valve S1 (OFF) 1st/ Except 1st Secondary Regulator Valve Line Pressure Orifice B Secondary Pressure Orifice Switching Control ON/OFF 1-2 Shift Valve Solenoid Valve S4 (ON) Line Pressure Orifice A Lubrication SL1 Relay Valve Orifice B 259LSK68