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

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.

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.

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.

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.

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.