Engine Start

Engine Start

When the vehicle is operating with the internal combustion engine OFF and auxiliary fluid pump ON, and the HPCM determines that vehicle operating conditions (low state of battery charge) are appropriate for starting the internal combustion engine (ICE), it commands the following changes to the transmission's hydraulic and electrical systems.

Note: The illustration shown depicts an Engine Start event that occurs during vehicle operation in Park. However, Engine Start can occur in any transmission operating range.

Torque Dampener Clutch Applies

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is energized (ON) allowing actuator feed limit fluid to enter the PCS 5 signal circuit. PCS 5 signal fluid is then routed through orifice #13 to the dampener bypass clutch valve.

Dampener Bypass Clutch Valve

PCS 5 signal fluid, at the dampener bypass clutch valve, opposes dampener bypass clutch valve spring force and orificed dampener clutch fluid pressure to regulate line or auxiliary line pressure into the dampener clutch circuit. Dampener clutch fluid is routed to the torque dampener clutch.

Torque Dampener Clutch Assembly

A feed hole in the input shaft allows fluid to enter the torque dampener assembly behind the torque dampener clutch piston. Dampener clutch fluid pressure moves the dampener clutch piston against spring force to apply the dampener clutch plates. When fully applied, the dampener clutch apply plate, the dampener clutch plates, and the dampener clutch plate assemblies are locked together, forming a direct mechanical connection between the engine flywheel and the transmission input shaft. With the engine flywheel and transmission input shaft locked together, the HPCM is able to use the generator/drive motor - unit A (107, 108) to start the ICE. The torque dampener clutch may be applied in any range when the vehicle is operating with the internal combustion engine OFF.

1-3 Reverse Clutch Applies

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #18 to the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Regulator Valve

PCS 4 signal fluid, at the 1-3 reverse clutch regulator valve, opposes 1-3 reverse clutch regulator valve spring force and 13 reverse clutch feedback fluid pressure to regulate line or auxiliary line pressure into the 13 reverse clutch/A cooling feed circuit.

#3 Ball Check Valve

13 reverse clutch feedback fluid unseats the #3 ball check valve, allowing excess pressure to pass into the actuator feed limit circuit. This helps to control clutch apply fluid pressure and clutch apply feel.

Shift Solenoid Valve - Mode A

13 reverse clutch/A cooling feed fluid passes through the shift solenoid valve - mode A and enters the 13 reverse clutch circuit.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid passes through the case and the transmission fluid pump cover into the 1-3 reverse clutch housing and moves the 1-3 reverse clutch piston against spring force to apply the 1-3 reverse clutch plates.

#1 Pressure Switch

Solenoid 2 signal fluid passes through the 1-3 reverse 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 Engine Start.

Shift Accumulation

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid is also sent to the 1-3 reverse clutch accumulator assembly. 13 reverse clutch fluid moves the 1-3 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the 1-3 reverse clutch assembly.

Engine Start