EVT Mode High is used to maximize engine efficiency and fuel economy under most normal driving conditions. The TCM processes input signals from the input and output speed sensors, the TP sensor and other vehicle sensors to determine the precise moment to command OFF the shift sloenoid 1 and the normally high pressure control solenoid 3 trim, and shift the transmission into EVT Mode High.

Pressure Control (PC) Solenoid 3 Trim

The PC solenoid 3 trim is commanded OFF, allowing PCS 3 signal fluid to exhaust from the hybrid low, 1-2 clutch regulator valve; the hybrid low, 1-2 clutch boost valve; and the shift solenoid valve - mode B.

Shift Solenoid 1

The shift solenoid 1 is commanded OFF, allowing solenoid 1 signal fluid to exhaust from the shift solenoid valve - mode A, the hybrid direct, 2-3-4 clutch regulator valve, and the 1-3 clutch regulator valve.

4th Clutch Assembly

4th clutch fluid pressure exhausts through the case assembly, allowing 4th clutch spring force to move the 4th clutch piston and release the 4th clutch plates.

Shift Solenoid Valve - Mode A

Shift solenoid valve - mode A spring force moves the shift solenoid valve - mode A to the released position, allowing 4th clutch fluid pressure to exhaust through the valve into the backfill circuit.

Hybrid Low, 1-2 Clutch Boost Valve

Hybrid low, 1-2 clutch boost valve spring force moves the hybrid low, 1-2 clutch boost valve to the released position, allowing HL 12 clutch/4th clutch feedback fluid pressure to exhaust into the HL 12 clutch/4th clutch feed circuit.

Hybrid Low, 1-2 Clutch Regulator Valve

Hybrid low, 1-2 clutch regulator valve spring force moves the hybrid low, 1-2 clutch regulator valve to the released position, allowing excess backfill pressure to exhaust through the valve into the HL 12 clutch/4th clutch feed circuit.

Shift Solenoid Valve - Mode B

Exhausting HL 12 clutch/4th clutch feed fluid pressure is routed to the shift solenoid valve - mode B, where it passes through the valve into the 4th clutch/B cooling feed circuit. 4th clutch/B cooling fluid pressure then passes through the shift solenoid valve - mode A to feed the B cooling circuit.

Clutch Piston Exhaust Blowoff Ball Valve

Excess fluid pressure in the backfill circuit exhausts at the clutch piston exhaust blowoff ball valve in order to maintain a constant backfill fluid pressure of 2 psi.

#3 Pressure Switch

With the actuator feed limit/backfill passage closed at the shift solenoid valve - mode A, actuator feed limit/backfill fluid pressure increases to actuator feed limit pressure. PS3 fluid pressure, fed by actuator feed limit/backfill pressure through the hybrid direct, 2-3-4 clutch regulator valve, also increases. PS3 fluid opens the normally closed #3 pressure switch, signaling the TCM that the transmission is in EVT Mode High.

#1 Pressure Switch

Actuator feed limit fluid passes through the hybrid low, 1-2 clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signaling the TCM that the transmission is in EVT Mode High.

#4 Pressure Switch

Actuator feed limit/backfill fluid pressure passes through the 1-3 clutch regulator valve into the PS4 fluid passage. PS4 fluid opens the normally closed #4 pressure switch, signaling the TCM that the transmission is in EVT Mode High.