Automatic Transmission - 2ml70 - Description and Operation Cadillac Escalade GMT900

Driver Shift Control

Driver shift control (DSC) allows the driver to change gears similar to a manual transmission.

Scheme 176

Transmission General Description

The Hybrid Two-Mode 2ML70 is a fully automatic, variable-speed, rear-wheel drive, electronic-controlled transmission. It consists primarily of a torque dampener assembly, an integral fluid pump and converter housing, 3 planetary gear sets, 2 friction (rotating) and 2 mechanical (stationary) clutch assemblies, and a hydraulic pressurization and control system, and 2 internal concentric 60 KW electric motors.

The torque dampener contains an internal torsional springs, fluid, input shaft. The torque dampener acts as a spring coupling to smoothly transmit power from the engine flexplate to the transmission. The dampener provides a mechanical direct drive coupling of the engine to the transmission.

The planetary gear sets provide 4 fixed gear ratios and the 2 EVT forward modes rations and reverse. Changing gear ratios is fully automatic and is accomplished through the use of a transmission control module (TCM) located inside the transmission and the hybrid powertrain control module (HPCM) located under the hood. Both the TCM and HPCM receives and monitors various electronic sensor inputs and uses this information to shift the transmission at the optimum time.

The TCM commands shift solenoids and variable bleed pressure control solenoids to control shift timing and feel. All the solenoids, including the TCM, are packaged into a self-contained control solenoid valve assembly.

The main hydraulic system primarily consists of a vane-type pump, 2 control valve body assemblies, converter housing and case. The pump maintains the working pressures needed to stroke the clutch pistons that apply or release the friction components. These friction components, when applied or released, support the automatic shifting qualities of the transmission.

The hydraulic system also uses a secondary system and consists of an auxiliary pump attached to the bottom of the transmission. This is a gerotor-type pump, electric 3 phase 12 volt motor, electric harness, and control module. This pump maintains working pressures when the engine is off.

The friction components used in this transmission consist of 4 multiple disc clutches. The multiple disc clutches combine with a planetary gear set and electric motor to deliver the different gear ratios, forward and 1 electric reverse. The gear sets then transfer torque through the output shaft.

The transmission may be operated in any of the following gear ranges

Transmission Component and System Description

The mechanical components of the Hybrid Two-Mode 2ML70 Transmission are as follows

1. Torque dampener assembly
2. Vane-type main fluid pump assembly
3. Gerotor type auxiliary fluid pump assembly
4. Input shaft and internal assembly
5. Sun gear carrier assembly first position
6. Drive motor with generator assembly first position
7. Drive motor with generator assembly second position
8. Internal gear assembly second position
9. Sun gear carrier assembly second position
10. 1-3 clutch housing assembly
11. Main shaft assembly
12. Center support assembly
13. Output shaft assembly
14. Control valve body assembly

The electrical components of the Hybrid Two-Mode 2ML70 are as follows

1. Two 60 KW electric concentric motors
2. Output speed sensor assembly
3. Manual shift shaft position switch
4. Control solenoid valve assembly, which contains the following components: Transmission control module (TCM) 5 variable bleed line pressure control (PC) solenoids Transmission fluid pressure (TFP) switch assembly 2 shift solenoids

For more information, refer to Electronic Component Description .

Transmission Adaptive Functions

The transmission utilizes a line pressure control system during upshifts to compensate for the normal wear of transmission components. As the apply components within the transmission wear or change over time, shift time (the time required to apply a clutch) will increase or decrease. In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids, to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as "adaptive learning" and it is used to ensure consistent shift feel plus increase transmission durability. The TCM monitors the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel.

The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle.

Transmission Indicators and Messages

The following transmission-related indicators and messages may be displayed on the instrument panel cluster (IPC). For a complete listing and description of all vehicle indicators and messages, refer to Indicator/Warning Message Description and Operation .

Scheme 177

Hybrid Transmission

The Hybrid transmission contains two electric drive motor with generator assemblies, 3 planetary gear sets, and 4 wet-plate clutches. The hybrid transmission can operate in either two electronically variable transmission (EVT) modes or one of four fixed gear ratios. The two permanent magnet electric motors are packaged within the transmission which is installed longitudinally in the vehicle. Three high voltage A/C cables, connected to each of the two motors, attach to transmission housing and are routed via rigid conduit around the transmission then transition to flexible cable at the attachment to the drive motor generator control module (DMGCM) Transmission fluid is used for hydraulic control and transmission component and motor cooling. An auxiliary oil pump is mounted externally to the transmission and provides oil pressure during engine-off Auto-Stop operation.

Scheme 178

Two permanent magnet electric motors mounted inside the transmission enable engine cranking, transmission reverse, and two EVT modes of operation. The front, or motor 1 and the rear, or motor 2 each provide 60kW peak power. Both are actively cooled via transmission fluid and are encased in steel housings to facilitate transmission assembly. The front motor is used to start the engine and also react torque from the rear motor. The rear motor propels the vehicle when operating in full-electric mode with the engine off or in reverse. Motor speeds are controlled and monitored by position sensors internal to the motor housings. The drive motor generator position sensor is monitored by the motor control module (MCM). The MCM monitors the angular position, speed and direction of the drive motor generator based upon the signals of the resolver-type position sensor. The position sensor (or resolver) contains a drive coil, two driven coils and an irregular shaped metallic rotor. The metallic rotor is mechanically attached to the shaft of the drive motor generator. At ignition ON, the MCM outputs a 5 volt ac, 10 kHz excitation signal to the drive coil. The drive coil excitation signal creates a magnetic field surrounding the two driven coils and the irregular shaped rotor. The MCM then monitors the two driven coil circuits for a return signal. The position of the irregular shaped metallic rotor causes the magnetically-induced return signals of the driven coils to vary in size and shape. A comparison of the two driven coils signals allows the MCM to determine the exact angle, speed and direction of the drive motor generator. For more information on the drive motor function and system interaction refer to Drive Motor Generator Control Module Description and Operation and Drive Motor Battery System Description .

Scheme 179

The control solenoid (w/body and TCM) valve assembly contains the following components

1. Transmission control module (TCM)
2. Clutch pressure control solenoids (Clutch PC Sol)
3. Shift solenoids (SS)
4. Line pressure control solenoid (Line PC Sol)
5. Transmission fluid temperature sensor (TFT Sensor)
6. TCM temperature sensor
7. Power-up temperature sensor (not used)
8. Transmission fluid pressure switches (TFP Sw)

These components are not serviced separately. The control solenoid (w/body and TCM) valve assembly utilizes a lead-frame system to connect these components electrically to the TCM. No wires are used for these components. The control solenoid (w/body and TCM) valve assembly bolts directly to the lower and upper valve body assemblies inside the transmission. The control solenoid (w/body and TCM) valve assembly connects to the engine harness 16-way connector via a pass-thru sleeve.

Scheme 180

The auxiliary oil pump is driven by a 12V AC motor controlled by a dedicated auxiliary fluid pump control module that is mounted in the engine compartment. Control of the auxiliary fluid pump is managed by the HPCM, which communicates directly with the auxiliary fluid pump control module. The purpose of the auxiliary fluid pump is to supply oil to the transmission for lube, cooling and clutch application during Auto-stop when the engine is off and the main transmission pump is not operating. The auxiliary fluid pump is commanded on when propulsion is active, such as when the vehicle is in electric only or stopped at a traffic light.

Scheme 181

The internal mode switch (IMS) assembly is a dual sliding contact switch attached to the control valve body within the transmission. The nine outputs from the switch indicate which position is selected by the transmission manual shaft. Four outputs (A, B, C, P), are range selection inputs to the transmission control module (TCM). Five outputs (R1, R2, D1, D2, S) are direction selection inputs to the HPCM through the transmission 24-way connector. The input voltage at the modules is high when the switch is open and low when the switch is closed to ground. The state of each input is displayed on the scan tool as IMS Range and IMS Direction. The IMS Range input parameters represented are transmission range signal A, signal B, signal C and signal P. The IMS Direction input parameters represented are transmission direction signal R1, signal R2, signal D1, signal D2 and signal Start.

Scheme 182

The output speed sensor (OSS) assembly has 2 internal hall-effect type sensors, and is capable of sensing both speed and direction. The OSS mounts to the A/T rear case assembly and is connected to the control solenoid (w/body and TCM) valve assembly through a wire harness and connector. The sensor faces the hybrid direct, 2-3-4 clutch housing assembly machined teeth surface. The sensor receives 8.3-9.3 volts on the OSS supply voltage circuit from the transmission control module (TCM). As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft.

The two sensor elements in the OSS assembly are spaced approximately 1/2 a tooth apart.

1. When the vehicle is moving in a forward direction, sensor A detects a particular tooth before sensor B.
2. When the vehicle is moving in a reverse direction, sensor B detects a particular tooth before sensor A.

The electronics in the sensor combine the two signals and send a signal with a different pulse width. This signal is interpreted by the TCM for speed and direction and is transmitted through the GMLAN circuits to the engine control module (ECM) and the hybrid powertrain control module (HPCM). The ECM, HPCM, and TCM compare the OSS signal with the ABS wheel speed sensor signal. The HPCM also compares the output shaft direction with the drive motor 1 and drive motor 2 direction.

Electric Launch

Upon the driver removing their foot from the brake pedal and depressing the accelerator, the vehicle will launch in electric-only mode. Hybrid Low 1-2 Clutch is locked and motor 2 provides output torque to the wheels. Under low speed driving conditions the vehicle operates in full-electric mode without starting the engine or using drive motor 1. DC power from the battery flows to the HPCM where it is converted into 3-phase AC power to drive motor 2. The auxiliary oil pump runs to provide oil to the transmission for lubrication and hydraulic control. The vehicle continues to operate in electric-only mode, until additional power is required to accelerate the vehicle. At that point the engine starts.

EVT Mode 1

After the engine is started the system operates in EVT Mode 1 which is used for low speed urban driving conditions. Utilizing an input split configuration, engine simultaneously drives motor 1 to both generate electricity to charge the hybrid battery and provide power through the mechanical gearing in the transmission to the wheels. The energy generated by drive motor 1 is stored in the battery while drive motor 2 draws battery energy to provide additional output torque. Depending on driving conditions the engine will operate in either 4 or 8-cylinder mode to optimize fuel consumption while maintaining output power requirements. Combining EVT operation with Active Fuel Management (AFM) allows the engine to operate in 4-cylinder mode over a wider range of operating conditions than a non-hybrid vehicle. EVT and AFM are synergistic technologies that enable greater fuel economy when combined together than when either technology is used independently. Drive motor 2 provides output power to augment the engine in 4-cylinder mode and drive motor 1 can be used to provide torque smoothing.

EVT Mode 2

As vehicle speed increases, the system shifts to EVT Mode-2. EVT Mode 2 uses a compound split configuration to transfer power through the transmission during higher speed operating conditions such as highway cruising. Similar to EVT Mode 1, engine power is used to both generate electricity through the motors and provide output torque via the mechanical gearing in the transmission. A synchronous shift point allows the 2-Mode transmission to shift between EVT Mode 1 and Mode 2 without changing speed.

Fixed Gear Operation

Fixed gear operation is achieved by selectively locking Clutches in the transmission to transmit engine power through a mechanical path without the use of the drive motors. Advantages of having fixed ratios include the ability to increase engine size without having to increase motor size and improved towing, climbing, and maximum acceleration performance which are particularly important. In fixed gear modes the drive motors can be used entirely for power assist, rather than partially to carry power through the transmission. Furthermore, the drive motors can be partially powered down during cruising conditions.

Regenerative Braking

Regenerative braking is enabled in both EVT Mode 1 and Mode 2. As the driver lifts their foot from the accelerator pedal and depresses the brake pedal the electric motors are used to decelerate the vehicle by applying negative torque to the output shaft and generate electricity thereby charging the battery. The 3-phase AC power generated by the motor is converted to high-voltage DC power in the HPCM and stored in the battery. The Hybrid Operating System coordinates requests for negative torque requests from the electronic brake module with electric motor and engine control functions.

Engine Start-Stop

As the driver depresses the accelerator pedal further, demanding increased vehicle acceleration, drive motor 1 is used to start the engine while the Hybrid Low 1-2 Clutch remains locked and motor 2 simultaneously provides output power to the wheels. During the engine start event motor 1 also provides active damping to reduce torque disturbances from engine cylinder firing pulses, and motor 2 is used to damp driveline disturbances. During this event the inverter draws DC power from the battery and converts it to AC power for both motors. They HPCM controls each motor's speed and power independently. The HPCM determines when to stop the engine and when to restart based on vehicle operating conditions and optimal hybrid battery power and fuel consumption. The engine is stopped at idle and during deceleration maneuvers to improve fuel economy.

Reverse

When the vehicle is placed in reverse the Hybrid Low 1-2 Clutch is locked and Motor 2 spins backwards and provides output torque to the wheels. When needed the engine starts and Motor 1 is used to charge the hybrid battery and DC power from the battery flows to the HPCM where it is converted into 3-phase AC power to drive motor 2.

Scheme 183

The transmission electrical connector is an important part of the transmission operating system. Any interference with the electrical connection can cause the transmission to set diagnostic trouble codes or affect proper operation. The following items can affect the electrical connection

1. Bent pins in the connector from rough handling during connection and disconnection
2. Wires backing away from the pins or coming uncrimped, in the external wiring harness
3. Dirt contamination entering the connector when disconnected
4. Transmission fluid leaking into the connector, wicking up into the external wiring harness and degrading the wire insulation
5. Moisture intrusion in the connector
6. Low pin retention in the external connector from excessive connection and disconnection of the wiring connector assembly
7. Pin corrosion from contamination
8. Damaged connector assembly

Remember the following points

1. Limit twisting or wiggling the connector during removal. Bent pins can occur.
2. Do not pry the connector off with a screwdriver or other tool.
3. Whenever the transmission external wiring connector is disconnected from the internal harness and the ignition is ON, DTCs will set. Clear these DTCs after reconnecting the external connector.

Use the following procedure to disconnect the engine side of the 16-way connector from the transmission side

1. Unlock the slide lock on the engine wiring harness connector.
2. Rotate the connector lever counterclockwise and remove the connector from the electrical connector passage sleeve.

Use the following procedure to reconnect the engine side of the 16-way connector to the transmission side

1. Orient the alignment slot on the engine side of the connector with the alignment tab on the electrical connector passage sleeve.
2. Slide the engine side connector through the electrical connector passage sleeve and into the transmission side connector.
3. Rotate the connector lever clockwise until the connector is fully seated.
4. Lock the slide lock on the connector.

Scheme 184

The transmission electrical connector is an important part of the transmission operating system. Any interference with the electrical connection can cause the transmission to set diagnostic trouble codes or affect proper operation. The following items can affect the electrical connection

1. Bent pins in the connector from rough handling during connection and disconnection
2. Wires backing away from the pins or coming uncrimped, in the external wiring harness
3. Dirt contamination entering the connector when disconnected
4. Transmission fluid leaking into the connector, wicking up into the external wiring harness and degrading the wire insulation
5. Moisture intrusion in the connector
6. Low pin retention in the external connector from excessive connection and disconnection of the wiring connector assembly
7. Pin corrosion from contamination
8. Damaged connector assembly

Remember the following points

1. Limit twisting or wiggling the connector during removal. Bent pins can occur.
2. Do not pry the connector off with a screwdriver or other tool.
3. Whenever the transmission external wiring connector is disconnected from the internal harness and the ignition is ON, DTCs will set. Clear these DTCs after reconnecting the external connector.

Use the following procedure to disconnect the engine side of the 24-way connector from the transmission side

1. Rotate the connector collar counterclockwise.
2. Remove the connector from the electrical connector passage sleeve.

Use the following procedure to reconnect the engine side of the 24-way connector to the transmission side

1. Orient the alignment slot on the engine side of the connector with the alignment tab on the electrical connector passage sleeve.
2. Slide the engine side connector through the electrical connector passage sleeve and into the transmission side connector.
3. Rotate the connector collar clockwise until the connector is fully seated.

Park - Engine Running

When the gear selector lever is in the Park (P) position and the engine is running, fluid is drawn into the fluid pump and line pressure is directed to the pressure regulator valve.

Backfill Fluid Circuit

Fed by fluid from the actuator feed limit circuit, through orifices #21, 22, 23, and 24, the backfill circuit is always filled with low pressure fluid. This fluid fills the various clutches and their supply circuits in preparation for a shift. Fluid pressure is not strong enough to move the clutch pistons against spring pressure, but fills the circuits allowing for quick pressurization and fast clutch apply when the TCM determines that conditions are appropriate to apply a clutch.

Clutch Piston Exhaust Blowoff Ball Valve

Backfill fluid is constantly limited to a pressure of 2 psi by the action of the clutch piston exhaust blowoff ball valve. When fluid pressure in the backfill circuit begins to exceed 2 psi, the ball moves against spring pressure allowing the excess fluid pressure to exhaust into the sump.

Hybrid Low, 1-2 Clutch Regulator Valve

Line or auxiliary line fluid is routed through orifice #9 to the hybrid low, 1-2 clutch regulator valve in preparation for a shift.

1-3 Clutch Regulator Valve

Line or auxiliary line fluid is routed through orifice #11 to the 1-3 clutch regulator valve in preparation for a shift.

Hybrid Direct, 2-3-4 Clutch Regulator Valve

Line or auxiliary line fluid is routed through orifice #10 to the hybrid direct, 2-3-4 clutch regulator valve in preparation for a shift.

Auxiliary Line Boost Valve

Line or auxiliary line fluid is routed through orifice #12 to the auxiliary line boost valve in preparation for a shift to EVT mode.

Scheme 185

EVT Mode Reverse - Engine Running

When the gear selector lever is moved to the Reverse (R) position (from the Park position) the following changes occur in the transmission's hydraulic and electrical systems

Pressure Control (PC) Solenoid 3 Trim

The PC solenoid 3 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #34 to the hybrid low, 1-2 clutch regulator valve; through orifice #33 to the hybrid low, 1-2 clutch boost valve: and to the shift solenoid valve - mode B.

PCS 3 signal fluid, at the hybrid low, 1-2 clutch regulator valve, opposes hybrid low, 1-2 clutch regulator valve spring force and HL 12 clutch/4th clutch feedback fluid pressure to regulate line or auxiliary line pressure into the HL 12 clutch/4th clutch feed circuit.

Hybrid Low, 1-2 Clutch Boost Valve

PCS 3 signal fluid pressure acts on a differential area of the hybrid low, 1-2 clutch boost valve, moving the valve against hybrid low, 1-2 clutch boost valve spring force to regulate HL 12 clutch/4th clutch feed fluid into the HL 12 clutch/4th clutch feedback circuit. As PCS 3 signal fluid pressure is increased to a given value, the hybrid low, 1-2 clutch boost valve opens the HL 1-2 clutch/4th clutch feedback circuit to exhaust. This results in the hybrid low, 1-2 clutch regulator valve moving to the full feed position, sending full HL 12 clutch/4th clutch feed pressure (full line pressure) to the hybrid low, 1-2 clutch.

Shift Solenoid Valve - Mode B

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

Hybrid Low, 1-2 Clutch Assembly

HL 12 clutch fluid pressure enters the rear case assembly behind the hybrid low, 1-2 clutch piston and moves the piston against spring force to apply the hybrid low, 1-2 clutch plates.

Scheme 186

EVT Mode Reverse - Engine Off

When the transmission is operating in EVT Mode Reverse (R), and the HCM determines that operating conditions are appropriate, the internal combustion engine is turned OFF, the auxiliary fluid pump is turned ON, and the TCM commands the following changes to the transmission's hydraulic and electrical systems.

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 #41 to the auxiliary line boost valve.

PCS 5 signal fluid, at the auxiliary line boost valve, opposes auxiliary line boost valve spring force and orificed auxiliary line boost fluid pressure to regulate line or auxiliary line pressure into the auxiliary line boost circuit. Auxiliary line boost fluid is routed to the fluid pump & auxiliary fluid pump valve in order to regulate auxiliary line fluid pressure.

Line Pressure Control (PC) Solenoid

The line PC solenoid is de-energized (OFF) allowing PCS line fluid pressure to exhaust through the solenoid.

With the exception of the switch to auxiliary line fluid pressure from the auxiliary fluid pump, no other changes occur to the transmission's hydraulic system and the hybrid low, 1-2 clutch remains applied.

Scheme 187

Neutral - Engine Running

When the gear selector is moved to the Neutral (N) position, the hydraulic and electrical system operation is identical to Park (P) range. However, if Neutral is selected after the vehicle was operating in Reverse (R), the following changes would occur in the hydraulic system

The PC solenoid 3 trim is de-energized (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.

HL 12 clutch fluid exhausts from the hybrid low, 1-2 clutch to the shift solenoid valve - mode B allowing the hybrid low, 1-2 clutch to release.

HL 12 clutch fluid passes through the shift solenoid valve - mode B and into the HL 12 clutch/4th clutch feed fluid circuit and is routed to the hybrid low, 1-2 clutch regulator 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 spring force moves the hybrid low, 1-2 clutch regulator valve to the released position, allowing HL 12 clutch/4th clutch feed fluid pressure to exhaust through the valve into the backfill circuit.

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.

Scheme 188

EVT Mode Low - Engine Running

When the gear selector lever is moved to the Drive (D) position from the Neutral (N) position, the following changes occur in the transmission's hydraulic and electrical systems in order to start the vehicle moving from a stopped position

The PC solenoid 3 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #34 to the hybrid low, 1-2 clutch regulator valve; through orifice #33 to the hybrid low, 1-2 clutch boost valve; and to the shift solenoid valve - mode B.

PCS 3 signal fluid, at the hybrid low, 1-2 clutch regulator valve, opposes hybrid low, 1-2 clutch regulator valve spring force and HL 12 clutch/4th clutch feedback fluid pressure to regulate line or auxiliary line pressure into the HL 12 clutch/4th clutch feed circuit.

PCS 3 signal fluid pressure acts on a differential area of the hybrid low, 1-2 clutch boost valve, moving the valve against hybrid low, 1-2 clutch boost valve spring force to regulate HL 12 clutch/4th clutch feed fluid into the HL 12 clutch/4th clutch feedback circuit. As PCS 3 signal fluid pressure is increased to a given value, the hybrid low, 1-2 clutch boost valve opens the HL 1-2 clutch/4th clutch feedback circuit to exhaust. This results in the hybrid low, 1-2 clutch regulator valve moving to the full feed position, sending full HL 12 clutch/4th clutch feed pressure (full line pressure) to the hybrid low, 1-2 clutch.

HL 12 clutch/4th clutch feed fluid is routed to the shift solenoid valve - mode B, where it passes through the valve in the HL 12 clutch circuit.

HL 12 clutch fluid pressure enters the rear case assembly behind the hybrid low, 1-2 clutch piston and moves the piston against spring force to apply the hybrid low, 1-2 clutch plates.

Scheme 189

EVT Mode Low - Engine Off

When the transmission is operating in EVT Mode Low (D), and the HPCM determines that operating conditions are appropriate, the internal combustion engine is turned OFF, the auxiliary fluid pump is turned ON, and the TCM commands the following changes to the transmission's hydraulic and electrical systems

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 #41 to the auxiliary line boost valve.

PCS 5 signal fluid, at the auxiliary line boost valve, opposes auxiliary line boost valve spring force and orificed auxiliary line boost fluid pressure to regulate line or auxiliary line pressure into the auxiliary line boost circuit. Auxiliary line boost fluid is routed to the fluid pump and auxiliary fluid pump valve in order to regulate auxiliary line fluid pressure.

The line PC solenoid is de-energized (OFF) allowing PCS line fluid pressure to exhaust through the solenoid.

With the exception of the switch to auxiliary line fluid pressure from the auxiliary fluid pump, no other changes occur to the transmission's hydraulic system and the hybrid low, 1-2 clutch remains applied.

Scheme 190

Drive Range, First Gear

When the gear selector lever is moved to the Overdrive Range (D) position from the Neutral (N) position, after the first 1-2 shift has occurred, the following changes occure to shift the transmission into Overdrive Range - First Gear

Pressure Control (PC) Solenoid 4 Trim

The PC solenoid 4 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #36 to the 1-3 clutch regulator valve.

Shift Solenoid 1

The shift solenoid 1 is energized, allowing actuator feed limit fluid to enter the solenoid 1 signal fluid circuit. Solenoid 1 signal fluid is routed to the shift solenoid valve - mode A. Solenoid 1 signal fluid is also routed to the hybrid direct, 2-3-4 clutch regulator valve where it enters the PS2 fluid circuit, and to the 1-3 clutch regulator valve where it enters the PS4 circuit.

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

#2 Encapsulated Ball Check Valve

13 clutch feedback fluid unseats the #2 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

Solenoid 1 signal fluid is routed to the shift solenoid valve - mode A and moves the valve against shift solenoid valve - mode A spring force to the applied position. This allows 13 clutch/A cooling feed fluid to enter the 13 clutch circuit.

1-3 Clutch Assembly

13 clutch fluid enters the transmission case assembly and moves the 1-3 clutch piston against spring force to apply the 1-3 clutch plates.

#3 Pressure Switch

Solenoid 1 signal fluid passes through the hybrid direct, 2-3-4 clutch regulator valve into the PS3 fluid passage. PS3 fluid opens the normally closed #3 pressure switch, signaling the TCM that the transmission is in Drive Range - First Gear.

#4 Pressure Switch

Solenoid 1 signal fluid 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 Drive Range - First Gear.

Scheme 191

Drive Range, Second Gear

As vehicle speed increases and operating conditions become appropriate, the transmission control module (TCM) processes input signals from the input and output speed sensors, the throttle position (TP) sensor and other vehicle sensors to determine the precise moment to de-energize or "turn OFF" the normally low pressure control solenoid 4 trim, to command ON the normally high pressure control solenoid 2 trim, and shift the transmission into Second Gear

The PC solenoid 4 trim is commanded OFF, allowing PCS 4 signal fluid to exhaust from the 1-3 clutch regulator valve.

13 clutch fluid pressure is exhausted from the center support assembly, allowing 1-3 clutch spring force to move the 1-3 clutch piston and release the 1-3 clutch plates.

Exhausting 13 clutch fluid pressure passes through the shift solenoid valve - mode A into the 13 clutch/A cooling feed circuit.

13 clutch feedback fluid pressure exhausts into the 13 clutch/A cooling feed circuit, allowing actuator feed limit fluid to seat the ball.

1-3 clutch regulator valve spring force moves the 1-3 clutch regulator valve to the released position, allowing 13 clutch/A cooling feed fluid pressure to exhaust through the valve into the backfill circuit.

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.

Pressure Control (PC) Solenoid 2 Trim

The PC solenoid 2 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 2 signal circuit. PCS 2 signal fluid is then routed through orifice #38 to the hybrid direct, 2-3-4 clutch regulator valve.

PCS 2 signal fluid, at the hybrid direct, 2-3-4 clutch regulator valve, opposes hybrid direct, 2-3-4 clutch regulator valve spring force and HD 234 clutch feedback fluid pressure to regulate line or auxiliary line pressure into the HD 234 clutch/B cooling feed circuit.

#1 Encapsulated Ball Check Valve

HD 234 clutch feedback fluid unseats the #1 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.

HD 234 clutch/B cooling feed fluid passes through the shift solenoid valve - mode A into the HD 234 clutch supply fluid circuit and is routed to the shift solenoid valve - mode B.

HD 234 clutch supply fluid passes through the shift solenoid valve - mode B into the HD 234 clutch circuit and is routed to the hybrid direct 2-3-4 clutch assembly.

Hybrid Direct, 2-3-4 Clutch Assembly

HD 234 clutch fluid is directed to the hybrid direct, 2-3-4 clutch piston to apply the hybrid direct, 2-3-4 clutch plates and achieve second gear.

HD 234 clutch/B cooling feed fluid is routed to the shift solenoid valve - mode B where it is blocked by the valve in preparation for an upshift to third gear.

Scheme 192

Drive Range, Third Gear

As vehicle speed increases and operating conditions become appropriate, the transmission control module (TCM) processes input signals from the input and output speed sensors, the throttle position (TP) sensor and other vehicle sensors to determine the precise moment to command ON the normally low pressure control solenoid 2 trim to regulate 1-3 clutch apply. At the same time the normally high pressure control solenoid 3 trim is commanded OFF, and the transmission shifts into Third gear.

The PC solenoid 4 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #36 to the 1-3 clutch regulator valve.

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

13 clutch feedback fluid unseats the #2 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.

Solenoid 1 signal fluid is routed to the shift solenoid valve - mode A and moves the valve against shift solenoid valve - mode A spring force to the applied position. This allows 13 clutch/A cooling feed fluid to enter the 13 clutch circuit.

13 clutch fluid enters the transmission case assembly and moves the 1-3 clutch piston against spring force to apply the 1-3 clutch plates.

Solenoid 1 signal fluid 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 Drive Range - Third Gear.

The PC solenoid 3 trim is de-energized (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 2

The shift solenoid 2 is energized, allowing actuator feed limit fluid to enter the solenoid 2 signal fluid circuit. Solenoid 2 signal fluid is routed through orifice #40 to the shift solenoid valve - mode B.

HL 12 clutch fluid exhausts from the hybrid low, 1-2 clutch to the shift solenoid valve - mode B allowing the hybrid low, 1-2 clutch to release.

Solenoid 2 signal fluid is routed to the shift solenoid valve - mode B and moves the valve against shift solenoid valve - mode B spring force to the applied position. This allows HL 12 clutch fluid pressure to exhaust through the valve into the backfill circuit. Also, HD 234 clutch/B cooling feed fluid replaces HD 234 clutch supply fluid, in order to feed the HD 234 clutch circuit and keep the hybrid direct, 2-3-4 clutch applied.

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

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.

#5 Pressure Switch

The applied shift solenoid valve - mode B closes off the PS5 circuit exhaust, allowing fluid pressure in the circuit to build to actuator feed limit fluid pressure. PS5 fluid opens the normally closed #5 pressure switch, signaling the TCM that the transmission is in Drive Range - Third Gear.

#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 Drive Range - Third Gear.

Actuator feed limit fluid passes through the hybrid low, 1-2 clutch regulator valve into the PS3 fluid passage. PS3 fluid opens the normally closed #3 pressure switch, signaling the TCM that the transmission is in Drive Range - Third Gear.

Scheme 193

Drive Range - Fourth Gear

As vehicle speed increases, 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 ON the normally high pressure control solenoid 3 trim to regulate 4th clutch apply. At the same time, the normally low pressure control solenoid 4 trim is commanded OFF and the transmission shifts into Fourth gear.

The PC solenoid 3 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #34 to the hybrid low, 1-2 clutch regulator valve; through orifice #33 to the hybrid low, 1-2 clutch boost valve; and to the shift solenoid valve - mode B.

PCS 3 signal fluid, at the hybrid low, 1-2 clutch regulator valve, opposes hybrid low, 1-2 clutch regulator valve spring force and HL 12 clutch/4th clutch feedback fluid pressure to regulate line or auxiliary line pressure into the HL 12 clutch/4th clutch feed circuit.

PCS 3 signal fluid pressure acts on a differential area of the hybrid low, 1-2 clutch boost valve, moving the valve against hybrid low, 1-2 clutch boost valve spring force to regulate HL 12 clutch/4th clutch feed fluid into the HL 12 clutch/4th clutch feedback circuit. As PCS 3 signal fluid pressure is increased to a given value, the hybrid low, 1-2 clutch boost valve opens the HL 1-2 clutch/4th clutch feedback circuit to exhaust. This results in the hybrid low, 1-2 clutch regulator valve moving to the full feed position, sending full HL 12 clutch/4th clutch feed pressure (full line pressure) to the hybrid low, 1-2 clutch.

Shift Solenoid - Mode B

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

4th Clutch Assembly

4th clutch fluid pressure enters the case assembly behind the 4th clutch piston and moves the piston against spring force to apply the 4th clutch plates.

The PC solenoid 4 trim is commanded OFF, allowing PCS 4 signal fluid to exhaust from the 1-3 clutch regulator valve.

13 clutch fluid pressure is exhausted from the center support assembly, allowing 1-3 clutch spring force to move the 1-3 clutch piston and release the 1-3 clutch plates.

Exhausting 13 clutch fluid pressure passes through the shift solenoid valve - mode A into the 13 clutch/A cooling feed circuit.

13 clutch feedback fluid pressure exhausts into the 13 clutch/A cooling feed circuit, allowing actuator feed limit fluid to seat the ball.

1-3 clutch regulator valve spring force moves the 1-3 clutch regulator valve to the released position, allowing 13 clutch/A cooling feed fluid pressure to exhaust through the valve in the backfill circuit.

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.

Scheme 194

EVT Mode High - From Drive Range 4th Gear

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 solenoid 1 and the normally high pressure control solenoid 3 trim, and shift the transmission into EVT Mode High.

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.

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 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 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 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 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.

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.

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.

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.

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.

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.

Scheme 195

Power Off Low Default

If the transmission is in First or Second gear during a transmission electrical component malfunction, the transmission will defualt to Low. All solenoids will default to their normal state. This default action enables the vehicle to be safely driven to a service center.

The PC solenoid 3 trim defaults to its normally high state (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #34 to the hybrid low, 1-2 clutch regulator valve; through orifice #33 to the hybrid low, 1-2 clutch boost valve; and to the shift solenoid valve - mode B.

PCS 3 signal fluid pressure acts on a differential area of the hybrid low, 1-2 clutch boost valve, moving the valve against hybrid low, 1-2 clutch boost valve spring force to block HL 12 clutch/4th clutch feed fluid from entering the HL 12 clutch/4th clutch feedback circuit, and opening the HL 12 clutch/4th clutch feedback circuit to exhaust. This results in the hybrid low, 1-2 clutch regulator valve moving to the full feed position, sending full HL 12 clutch/4th clutch feed pressure (full line pressure) to the hybrid low, 1-2 clutch.

PCS 3 signal fluid moves the hybrid low, 1-2 clutch regulator valve, against hybrid low, 1-2 clutch regulator valve spring force, to the applied position. This allows line or auxiliary line fluid to pass through the valve into the HL 12 clutch/4th clutch feed circuit.

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

HL 12 clutch fluid pressure enters the rear case assembly behind the hybrid low, 1-2 clutch piston and moves the piston against spring force to apply the hybrid low, 1-2 clutch plates.

1-3 Clutch Releases

If the transmission is operating in First gear when an electrical malfunction occurs, the normally closed shift solenoid 1 and the normally low pressure control solenoid 4 trim default to their normal states (OFF) and the 1-3 clutch is released. Refer to Drive Range, Second Gear for a complete description of 1-3 clutch release.

Hybrid Direct, 2-3-4 Clutch Releases

If the transmission is operating in Second gear when an electrical malfunction occurs, the shift solenoid 1 defaults to its normally closed state (OFF) and the hybrid direct, 2-3-4 clutch is released.

The shift solenoid 1 defaults to its normally closed state (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.

HD 234 clutch fluid pressure is exhausted from the rear case assembly, allowing hybrid direct, 2-3-4 clutch spring force to move the hybrid direct, 2-3-4 clutch piston and release the hybrid direct, 2-3-4 clutch plates.

Exhausting HD 234 clutch fluid pressure passes through the shift solenoid valve - mode B into the HD 234 clutch supply circuit.

Shift solenoid valve - mode A spring force moves the shift solenoid valve - mode A to the released position, allowing HD 234 clutch supply fluid pressure to exhaust through the valve into the backfill circuit.

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.

Scheme 196

Power Off High Default

If the transmission is in Third or Fourth gear during a transmission electrical component malfunction, the transmission will defualt to high. All solenoids will default to their normal state. The transmission will remain in Power Off High Default until the ignition has been turned off, or the transmission is shifted to Reverse (R). When the vehicle is restarted, and shifted back into Drive (D), the transmission will then operate in Power Off Low Default. This default action enables the vehicle to be safely driven to a service center.

The PC solenoid 3 trim defaults to its normally high state (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice #34 to the hybrid low, 1-2 clutch regulator valve; through orifice #33 to the hybrid low, 1-2 clutch boost valve; and to the shift solenoid valve - mode B.

The shift solenoid 2 defaults to its normally closed state (OFF), allowing solenoid 2 signal fluid to exhaust from the shift solenoid valve - mode B.

PCS 3 signal fluid pressure acts on a differential area of the shift solenoid valve - mode B, holding the valve in the applied position against shift solenoid valve - mode B spring force. This allows HD 234 clutch/B cooling feed fluid pressure to continue to feed the HD 234 clutch circuit.

HD 234 clutch fluid is directed to the hybrid direct, 2-3-4 clutch piston to apply the hybrid direct, 2-3-4 clutch plates.

If the transmission is operating in Third gear when an electrical malfunction occurs, the normally closed shift solenoid 1 and the normally low pressure control solenoid 4 trim default to their normal states (OFF) and the 1-3 clutch is released. Refer to Drive Range - Fourth Gear for a complete discription of 1-3 clutch release.

4th Clutch Releases

If the tranmission is operating in Fourth gear when an electrical malfunction occurs, the shift solenoid 1 defaults to its normally closed state (OFF) and the 4th clutch is released. Refer to EVT Mode High - From Drive Range 4th Gear for a complete description of 4th clutch release.

Scheme 197

Scheme 198

Scheme 199

Scheme 200

Scheme 201

Scheme 202

Scheme 203

Scheme 204

Scheme 205

Scheme 206

Scheme 207

Scheme 208

Scheme 209

Scheme 210

Scheme 211

Scheme 212

See also:
• Indicator/Warning Message Description and Operation
• Drive Motor Generator Control Module Description and Operation
• Drive Motor Battery System Description
• Electronic Component Description
• Drive Range, Second Gear
• Drive Range - Fourth Gear
• EVT Mode High - From Drive Range 4th Gear