Part 2 of 2
HYBRID ELECTRIC CONTROL SOFTWARECreep Mode
The hybrid electric system delivers torque to the wheels to mimic the creep normally found on vehicles equipped with an automatic transmission. The powertrain control module (PCM) commands a predetermined amount of torque to be delivered to the output shafts of the electronically controlled continuously variable transaxle (CVT). This torque is delivered from a combination of sources: the internal combustion engine, the traction motor, or the generator motor. The maximum creep speed in forward or reverse direction is about 6 km/h (4 mph). The creep speed may slightly vary if ambient temperature, altitude, relative humidity, engine temperature, or weight of the vehicle change.
Driving Modes
There are 5 fundamental operating modes in the hybrid electric system:
- electric mode
- positive split mode
- negative split mode
- neutral gear mode
- engine cranking mode
Electric Mode
Electric Mode:
The hybrid electric system operates in the electric mode when the vehicle is propelled by the electrical power stored in the high voltage traction battery. The torque is supplied to the output shafts by the traction motor, the generator motor, or a combination of both. This is a preferred mode whenever the desired torque is low and the electrical system rather than the engine can produce it more efficiently. The electric mode is also used in reverse because the engine can only deliver torque in a forward direction.
Positive Split Mode
Positive Split Mode:
In this mode the internal combustion engine is running and powering the generator motor which produces the electricity. The power from the engine is split between the path through the generator motor and the path to the output shafts of the vehicle. The electricity produced by the generator motor charges the high voltage traction battery or powers the traction motor. In this mode the traction motor can operate as a motor or as a generator to make up the difference between engine power and desired power at the wheels. This mode is preferred whenever the traction battery needs to be charged.
Negative Split Mode
Negative Split Mode:
In this mode the internal combustion engine is running but the generator motor is reducing the engine speed. This mode is never preferred but occurs when all of the following vehicle conditions are met:
- the engine is running.
- the vehicle speed is high.
- the high voltage traction battery is charged.
- reducing engine throttle is not desired.
Neutral Gear Mode
The hybrid electric system operates in this mode when the driver selects NEUTRAL. In neutral gear the electronically controlled continuously variable transaxle (CVT) does not deliver any positive or negative torque to the output shafts of the vehicle. The neutral gear actually consists of 2 neutral operating states: active neutral activated above 10 km/h (6 mph), and passive neutral activated below 10 km/h (6 mph). In active neutral, the generator motor is permitted to start and stop the internal combustion engine as needed to maintain the high voltage traction battery charge, and provide A/C. In passive neutral, the engine must remain in the state it was (running or not running) when the mode was entered and is not permitted to change state (start or stop). If the engine is running when entering passive neutral, the speed control of the engine is transferred from the generator motor to the engine itself. The engine controlling its own speed in passive neutral is described as secondary idle. The vehicle cannot be started in passive neutral, but can be started in active neutral.
Engine Cranking Mode
Engine Cranking Mode:
The electronically controlled continuously variable transaxle (CVT) provides the engine cranking function to start or restart the internal combustion engine. When the powertrain control module (PCM) requests the engine cranking mode, the generator motor rapidly accelerates the engine speed up to about 1,000 RPM in about 0.3 seconds. When the engine speed reaches a calibrated speed the PCM commands the delivery of fuel and spark at the appropriate times.
Limited Operating Strategy (LOS) Modes
For some hybrid electric system malfunctions the powertrain control module (PCM) may initiate one or more of the LOS modes. The objective of the LOS modes is to manage vehicle operation after one or more of the following systems are disabled due to a malfunction: engine, electronically controlled continuously variable transaxle (CVT), traction battery, or regenerative brake system. Some LOS modes limit the vehicle capability to a limp home condition. Other LOS modes fully disable the vehicle. The PCM initiates the appropriate LOS mode depending on the severity of the malfunction that was detected.
When the PCM detects system faults for which the LOS mode is initiated, it stores a corresponding diagnostic trouble code (DTC). The root cause of the malfunction that initiated the LOS mode may be in a different subsystem or component than indicated by the DTC. Therefore, these DTCs should be considered LOS or FMEM only and are always assisted by the other, more detailed, circuit DTCs. The circuit DTCs should always be used to diagnose the problem before LOS or FMEM DTCs. LOS or FMEM DTCs do not mean that the subsystem or component they describe actually failed, but indicate the subsystem or component that is effected by the LOS mode.
- P1A0C Hybrid Powertrain Control Module - Engine Disabled
- P1A0D Hybrid Powertrain Control Module - Generator Disabled
- P1A0E Hybrid Powertrain Control Module - Traction Motor Disabled
- P1A0F Hybrid Powertrain Control Module - Vehicle Disabled
- P1A10 Hybrid Powertrain Control Module - Traction Battery Disabled
- P1A13 Hybrid Powertrain Control Module - Regenerative Braking Disabled
- P1A14 Hybrid Powertrain Control Module - Transmission Disabled
High Speed Control Area Network (CAN)
For information on high speed CAN, refer to Powertrain Control Software, High Speed Control Area Network (CAN). Powertrain Control Software
Multiplexing
For information on multiplexing, refer to Powertrain Control Software, Multiplexing. Powertrain Control Software
Multiplexing Implementation
For information on multiplexing implementation, refer to Powertrain Control Software, Multiplexing Implementation. Powertrain Control Software
Normal Power Down Sequence
The powertrain control module (PCM) must conduct a normal power-down sequence. Whenever the key is turned to the OFF or ACC position, modules that are powered up by the RUN circuit immediately shut down. However the PCM, transaxle control module (TCM), and the traction battery control module (TBCM) stay on, until the power-down sequence is complete. The PCM keeps the TCM alive by controlling the power sustain relay (PSR) which provides power to the TCM. The TBCM is powered directly from the low voltage battery which permits wake-up function when the vehicle is off. During the power-down sequence the PCM:
- cuts the power to injectors and ignition coils (engine shut down).
- requests the TCM to disable high voltage inverters.
- disables the DC/DC converter.
- requests the TBCM to open the high voltage contactors.
- requests the TCM to discharge the high voltage inverter capacitors.
- opens the power sustain relay.
If the power down sequence does not execute correctly, it is considered an abnormal shut-down, which may result in the PCM, the TCM and the TBCM storing diagnostic trouble codes (DTCs).
Power Up Sequence
The powertrain control module (PCM) must conduct a power-up sequence every time the key is turned from the OFF to the START position. The power-up sequence is carried out only with the electronically controlled continuously variable transaxle (CVT) gear selector in the PARK position. During the power-up sequence the PCM:
- initializes and begins CAN communications with the transaxle control module (TCM) and the traction battery control module (TBCM).
- checks for TCM error status.
- requests the TBCM to close the high voltage contactors.
- enables the DC/DC converter.
- starts the internal combustion engine.
If the malfunction is detected during the power up sequence, the PCM may initiate LOS mode and store diagnostic trouble codes (DTCs).
Regenerative Braking
Regenerative Braking:
The regenerative braking is a software strategy and is controlled by the powertrain control module (PCM), the transaxle control module (TCM), and the traction battery control module (TBCM). Regenerative braking is the ability to capture and store a portion of the energy that would be lost as heat during a braking event. When the driver uses the brakes, the PCM determines how much negative torque (braking force) the traction motor should provide in addition to the friction brakes. Depending on the high voltage traction battery state of charge, the amount of negative torque provided by traction motor can vary between 0 and 100 percent. The traction motor then becomes a generator, which causes the energy to flow into the high voltage traction battery. The PCM strategy smoothly blends regenerative and friction brake effort to make the dual brake operation transparent to the driver.
Torque Monitor
The torque monitor resides within the powertrain control module (PCM) as both software and as a redundant safety processor. The torque monitor detects certain computer faults of the PCM. The torque monitor also detects if the overall powertrain torque delivered to the output shafts of the vehicle is excessive to what the driver is requesting. The torque monitor detects 3 gross errors that are present for some calibrated amount of time:
- unintended vehicle motion - the powertrain accelerates the vehicle when it should not (such as in NEUTRAL) or provides torque in the wrong direction.
- excess acceleration - vehicle accelerates at greater rate than the driver or the speed control requests.
- excess powertrain deceleration - vehicle powertrain braking exceeds driver demand.
When any of the gross errors are detected, the torque monitor communicates it to the PCM, which initiates appropriate action such as limited operating strategy (LOS) mode. The torque monitor requested LOS mode can be cleared when the malfunction is not present anymore, and the key is cycled to the OFF position for about 10 seconds.
Torque Determination and Energy Management
Torque Determination And Energy Management:
The powertrain control module (PCM) is responsible for torque determination and energy management functions. The PCM monitors gear selector position (PRNDL), brake pedal position (BPP) and accelerator pedal position (APPS). The PCM then makes a torque command determination. Positive torque is perceived as vehicle acceleration and negative torque is perceived as braking. Based on the amount of torque requested by the driver, the PCM decides which power source has to deliver the torque to meet the driver demand while the powertrain system is running most efficiently.
Vehicle System Controller (VSC)
The powertrain control module (PCM), transaxle control module (TCM), and traction battery control module (TBCM) are connected to a high speed controller area network (CAN) to exchange information messages. The VSC is a software function integrated inside the PCM, and is responsible for vehicle system operation, generating and sending commands to initiate appropriate actions such as limited operation strategy (LOS) modes when serious malfunction is detected. The PCM also stores diagnostic trouble codes (DTCs) along with the freeze frame PID related to the LOS action that was initiated. To retrieve DTCs from the PCM an on-demand and continuous memory self-test must be carried out.
HYBRID ELECTRIC CONTROL HARDWARE
DC/DC Converter
DC/DC Converter:
The purpose of the DC/DC converter is to function as an alternator in a conventional powertrain. The PCM controls operation of the DC/DC converter. Because the converter does not use any moving parts, the low voltage battery is charged when the vehicle drives with the engine ON or OFF. This is accomplished by converting power from the high voltage traction battery to a regulated output voltage of a nominal 14.5 volts, while supplying a load current of up to 110 amps. The PCM controls the DC/DC enable (DCE) hardwired signal to switch the DC/DC converter on and off. The DC/DC converter provides feedback to the PCM using the hardwired DC/DC fault (DCF) signal. The DCF signal indicates to the PCM when the converter is non-operation or when the malfunction occurred. The DC/DC converter is cooled by the motor electronics cooling system and is located on the passenger side in the engine compartment.
Hybrid Electric Indicators
The hybrid electric warning indicators alert the driver that a hybrid electric system malfunction is detected. There are 3 indicators dedicated to the hybrid electric system:
- over-temperature indicator
- caution indicator
- hazard indicator
Over-Temperature Indicator
Over-Temperature Indicator:
The PCM monitors the engine, the motor electronics coolant temperature (MECT), and the electronically controlled continuously variable transaxle (CVT) for an over-temperature condition. If either of the temperatures exceed their threshold value, the fail-safe cooling status changes status to ON, and the PCM broadcasts an over-temperature indicator on CAN message to the instrument cluster. The instrument cluster then illuminates the indicator light. The over-temperature indicator is extinguished when the temperature returns below the threshold value.
Caution Indicator (Yellow Wrench)
Caution Indicator:
The caution indicator is illuminated whenever a malfunction within the hybrid electric system is detected and a repair is needed. When the malfunction is present, the control module that detected the malfunction stores the DTC and broadcasts a caution on CAN message to the instrument cluster. Upon receiving the CAN message, the instrument cluster turns the indicator on.
Two actions can extinguish the caution indicator light:
- the module requesting the indicator ON is reset.
- the malfunction is not present anymore and the key is cycled.
If the caution indicator flashes at the once per second rate, it indicates that the vehicle is in the engine running diagnostic mode. Refer to Diagnostic Methods, Diagnostic Modes for engine running diagnostic mode. The caution indicator illuminates for 3 seconds during instrument cluster prove-out when the key is cycled from the OFF to the ON position. Diagnostic Modes
Hazard Indicator (Red Triangle)
Hazard Indicator:
The hazard indicator is illuminated whenever a severe malfunction within the hybrid electric system is detected and continued use of the vehicle is likely to cause damage to the system or to the vehicle. When the malfunction is present, the control module detects, sets the DTC and broadcasts a hazard on CAN message to the instrument cluster. Upon receiving the CAN message, the instrument cluster turns the indicator on.
Two actions can extinguish the hazard indicator light:
- the module requesting the indicator on is reset.
- the malfunction is not present anymore and the key is cycled.
If the hazard indicator flashes at the once per second rate, it indicates that the vehicle is in the engine cranking diagnostic mode. Refer to Diagnostic Methods, Diagnostic Modes for engine cranking diagnostic mode. The hazard indicator illuminates for 3 seconds during the instrument prove-out when the key is cycled from the OFF to the ON position. Diagnostic Modes
High Voltage Cables
WARNING: This vehicle is equipped with high voltage cables, components, and wiring. The high voltage warning labels containing the high voltage symbol are located on each high voltage component. High voltage cables, and wiring are orange in color. Certified rubber insulating gloves and a face shield must be worn when working with the high voltage cables, components, or wiring. The ignition key must be cycled to the OFF position for a minimum of 5 minutes, and the high voltage traction battery service disconnect plug placed In the servicing/shipping position before disconnecting the high voltage cables. Failure to follow these instructions may result In personal Injury or death. Do not disconnect, disable, or touch the high voltage cables, components, or wiring during the module reprogramming procedure because high voltage is present. The high voltage warning labels containing the high voltage symbol are located on each high voltage component. High voltage cables, and wiring are orange in color. Failure to follow these instructions may result in personal injury or death.
The high voltage cables connect the high voltage traction battery with the electronically controlled CVT, and the electronically controlled CVT with the DC/DC converter. The harness is orange and contains high voltage positive and high voltage negative wires. Each of the high voltage wires contains a corresponding high voltage interlock (HVIL) circuit.
High Voltage Interlock (HVIL) Circuit
High Voltage Interlock:
The HVIL circuit, used in conjunction with the front and rear inertia fuel shutoff (IFS) switches, disables the vehicle if a collision occurs or an open circuit fault in the high voltage connection is detected. The HVIL circuit is internal to the high voltage harness, which connects the traction battery, the CVT, and the DC/DC converter. The transaxle control module (TCM) and the traction battery control module (TBCM) monitor the HVIL circuit for a low battery voltage. Whenever that voltage drops below a calibrated threshold, the high voltage traction battery immediately opens its high voltage contactors, the electronically controlled CVT discharges the high voltage capacitors, and the TCM stores the DTC P0A0A. This action is initiated when the vehicle is disabled and cannot be driven.
Low Voltage Battery Power
The low voltage battery is used as a low voltage energy storage. The battery is charged by the DC/DC convener. For information on the DC/DC convener refer to Hybrid Electric Control Hardware, DC/DC converter. The low voltage battery functions are:
- the voltage stabilizer in the system
- the power source for the power distribution box
- the power source for all control modules
- the power source for the traction battery during the jump start procedure
Power Sustain Circuit
For information on the power sustain circuit, refer to Powertrain Control Module (PCM) Outputs, Power Sustain Relay (PSR). Powertrain Control Module (PCM) Outputs
Traction Battery Control Module (TBCM)
Refer to Hybrid Drive Systems, High Voltage Traction Battery for more information on TBCM and diagnostics.
Transaxle Control Module (TCM)
The microprocessor that controls operation of the electronically controlled continuously variable transaxle (CVT) is called the TCM. The TCM receives a variety of CAN messages and hardwired signals from modules connected to the CAN network. Based on information received, the TCM makes a decision on how to control the operation of the generator motor or the traction motor. In case of a malfunction the TCM is able to detect and store the appropriate diagnostic trouble code (DTC). To retrieve DTCs from the TCM, an on-demand and continuous memory self-test must be carried out.
NOTE: The TCM is a part of the electronically controlled CVT assembly and cannot be repaired as a separate component. Refer to Automatic Transmission/Transaxle for CVT repair procedures.
Transaxle Control Module (TCM) Keep Alive Memory (KAM)
The TCM stores information in KAM (a memory integrated circuit chip) about vehicle operating conditions, and then uses this information to compensate for component variability. KAM remains powered when the key is OFF so that this information is not lost.
TRANSAXLE CONTROL MODULE (TCM) INPUTS
Clean Tachometer Output (CTO)
For a complete description of the CTO refer to the Powertrain Control Module (PCM) Outputs Clean Tachometer Output (CTO). Powertrain Control Module (PCM) Outputs
Generator Shut Down (GSDN)
For a complete description of the GSDN refer to the Powertrain Control Module (PCM) Outputs Generator Shut Down (GSDN). Powertrain Control Module (PCM) Outputs
Immediate Shut Down (ISDN) 1 and 2
The TCM receives the redundant ISDN1 and ISDN2 signals from the high voltage traction battery. Under normal operating conditions the TCM monitors both ISDN circuits for low voltage battery voltage. If at any time during normal operation the TCM detects voltage drop on both ISDN circuits, the electronically controlled continuously variable transaxle (CVT) immediately stops delivering any torque, reduces operating voltage to under 50 volts, and discharges the high voltage capacitors. This action disables the vehicle until the key is cycled OFF and ON. The voltage drop on both ISDN circuits is usually a result of some other concern in the hybrid electric system, and DTCs indicating root cause may be stored in other modules. If the voltage drop is detected on only one of the ISDN circuits, the TCM continues its operation and stores the appropriate DTC. The voltage drop only on one of the ISDN circuits usually indicates an open ISDN circuit.
Motor Shut Down (MSDN)
For a complete description of the MSDN refer to the Powertrain Control Module (PCM) Outputs Motor Shut Down (MSDN). Powertrain Control Module (PCM) Outputs
TRANSAXLE CONTROL MODULE (TCM) OUTPUTS
Torque Of Generator-AC (TGAC) Signal
For a complete description of the TGAC refer to the Powertrain Control Module (PCM) Inputs Torque Of Generator-AC (TGAC) Signal. Powertrain Control Module (PCM) Inputs
Torque Of Motor-AC (TMAC) Signal
For a complete description of the TMAC refer to the Powertrain Control Module (PCM) Inputs Torque Of Motor-AC (TMAC) Signal. Powertrain Control Module (PCM) Inputs