Overview
The drive motor generator power inverter module (PIM) assembly converts high voltage direct current (DC) electrical energy to 3 phase alternating current (AC) electrical energy. The accessory DC power control module (APM) converts high voltage DC electric energy into low voltage (14V) and intermediate voltage (42V) in order to charge the vehicles accessory battery and supply electric energy to the 42V power steering system. The APM and PIM are fastened together and are referred to as the drive motor generator control module assembly. The drive motor generator control module assembly is cooled with pre-mixed Dexcool® circulating through a cooling system that is separate from the engine cooling system. The hybrid cooling system utilizes a heat exchanger at the front of the vehicle and electric pumps to circulate the coolant. The engine control module (ECM) monitors a temperature sensor in the hybrid cooling system and operates the radiator fan and the hybrid coolant pumps in response to system temperature.
High Voltage Circuits
Direct Current (DC)
The drive motor generator control module assembly is connected to each pole of the high voltage (HV), direct current (DC) drive motor generator battery. Both of the negative and positive HV DC battery poles are isolated from the vehicle chassis by a specific amount of resistance. Each HV DC cable is switched ON or OFF by a high voltage, high current contactor relay contained within the drive motor generator battery assembly. All HV DC negative and positive DC cables are individually shielded and orange in color to alert the technician to the potential presence of high voltage. The electric air conditioning compressor high voltage DC cables are externally connected at the drive motor generator control module assembly. The APM and PIM share an internal connection that supplies the APM with high voltage DC current.
Three Phase Alternating Current (AC)
Three cables connect each motor generator to the PIM. Each individually shielded cable is orange in color to alert the technician to the potential presence of high voltage.
Intermediate and Low Voltage Circuits
The APM converts high voltage 300V DC current into both intermediate voltage, 42V, and low voltage, 12V, current.
Intermediate Voltage 42V Direct Current
Intermediate voltage 42V cables are individually shielded and are blue in color to alert the technician to the potential presence of intermediate voltage.
Low Voltage (12V) Direct Current
Low voltage (12V) cables on the hybrid-electric vehicle do not require unique coloring or servicing procedures.
Drive Motor Generator Power Inverter Module (PIM) Assembly
Overview
Contained within the PIM assembly are the hybrid powertrain control module (HPCM), and two motor control modules (MCM). Each MCM controls its respective motor generator. All three modules are flash-programmable micro-processors.
Hybrid Powertrain Control Module (HPCM)
Location
The HPCM is a non-serviceable, flash-programmable micro-processor contained within the PIM assembly.
Operating Functions
The HPCM is the main controller of hybrid operation. The HPCM determines when to perform hybrid operation modes such as engine Auto-stop and regenerative braking. The HPCM also operates in conjunction with the battery energy control module (BECM) to determine when to enable and disable the DC high voltage circuits. Each MCM operates the applicable electric motor generator based upon HPCM commands.
Communication and Hosted Diagnostics
The HPCM is the host controller for diagnostic trouble code (DTC) information for the following control modules:
| • | Accessory DC power control module (APM) |
| • | Battery energy control module (BECM) |
| • | Motor control module (MCM) 1 |
| • | Motor control module (MCM) 2 |
| • | Auxiliary transmission fluid pump (ATFP) control module |
These modules diagnose their own operation and determine when a fault condition is present. Diagnostic status is communicated to the HPCM through the following circuits:
| • | APM utilizes the GM Hi-speed, Hybrid LAN communication circuit |
| • | BECM utilizes the GM Hi-speed, Hybrid LAN communication circuit |
| • | Each MCM and the HPCM exchange information and commands on the SPI bus internal communication circuit as well as the hi-speed hybrid GMLAN communication circuit. |
| • | ATFP control module utilizes a dedicated diagnostic status circuit |
In the event a hosted module communicates a fault condition, the HPCM will determine if hybrid operation is effected and notify the vehicle operator by requesting the MIL illuminate and/or by displaying a hybrid service required message. In addition, the HPCM will store the associated DTC information for retrieval by a scan tool. Some hosted modules may require an ignition cycle to clear certain DTCs from the HPCM.
Circuit Inputs
In addition to GMLAN parameters, the HPCM directly monitors the following signal circuits:
| • | Transmission shift selector internal mode switch (IMS) Direction and Park/Neutral switch signals |
| • | Engine crankshaft position (CKP) sensor signal |
| • | ATFP diagnostic circuit |
| • | High voltage interlock circuit (HVIC) |
Circuit Outputs
In addition to GMLAN and SPI bus commands, the HPCM directly controls the following output circuits:
| • | ATFP control circuit |
| • | BECM high voltage contactor relay pulse width modulated (PWM) control circuit |
Motor Control Module (MCM) 1 and 2
Location
Each electric motor generator located within the transmission assembly is controlled by its own motor control module (MCM) flash-programmable, micro-processor. Each MCM is contained within the PIM. Also contained within the PIM is the hybrid powertrain control module (HPCM) micro-processor.
Operating Functions
Each MCM operates the applicable electric motor generator based upon HPCM commands. Each MCM controls the speed, direction and output torque of its respective traction motor through the sequencing actuation of high current switching transistors called insulated gate bipolar transistors (IGBTs).
Communication and Hosted Diagnostics
In addition to the internal SPI bus communication circuit between the HPCM and each MCM, the MCMs also communicate on the Hi-speed and Hybrid GMLAN communication circuits. The MCM does not store its own diagnostic trouble code (DTC) information. The HPCM will store MCM associated DTC information for retrieval by a scan tool. The scan tool can communicate directly with each MCM in order to retrieve data parameters only.
Circuit Inputs
In addition to GMLAN parameters, each MCM monitors its respective motor generator for voltage, current, speed, direction and temperature. Additionally, the MCM monitors the IGBT components for temperature and proper operation. Some of the MCM operation data is shared with the HPCM.
Circuit Outputs
Each MCM controls its respective IGBT driver board that in-turn controls each motor generator. The motor generators operate using three-phase alternating current (AC) electricity. Three cables connect each motor generator to the PIM. Each individually shielded cable is orange in color to alert the technician that the potential for high voltage is present.
Accessory DC Power Control Module (APM)
Location
The APM is affixed to and located underneath the PIM. It is fastened to the PIM with external mounting fasteners and 2 internal high voltage circuit connection fasteners. The APM shares a coolant passage with the PIM and as such is gasketed to the PIM.
Operating Functions
The APM is the device which converts high voltage (300V) direct current (DC) to low voltage (12V) DC for accessory electrical operation and to charge the 12 volt accessory battery. The APM also converts HV DC to intermediate (42V) DC to supply the electric power steering system with voltage. The APM is capable of supplying up to 175 Amps of 12 volt DC and up to 50 Amps of 42 volt DC. In Jump Assist mode the APM converts 12 volt DC to HV DC to charge the high voltage hybrid batteries. The APM is capable of supplying up to 2.7 Amps at 290 volts DC on the high voltage circuit when operating in Jump Assist. An external 12V DC battery charger is required during the Jump Assist mode because the APM and vehicle controllers may draw as much as 80 Amps of current from the vehicles 12 volt DC system.
Communication and Hosted Diagnostics
The APM has internal diagnostic tests that run at both power-up and during operation. All DTCs from the APM are reported to and hosted by the HPCM. The APM communicates directly only with the HPCM and only on the high speed hybrid GMLAN communication circuit.
Circuit Inputs
Inputs supported by the APM include the high voltage and 12 volt circuits. The APM also monitors various internal components for current, voltage and temperature. The APM is also connected to the high speed hybrid GMLAN communication circuit. An individual 12 volt discrete circuit powers ON the APM. The APM will not begin conversion of voltage however, until the appropriate GMLAN enable signal is communicated to it by the HPCM.
Circuit Outputs
The only outputs supported by the APM are the 12 volt and 42 volt conversion during normal vehicle operation and high voltage conversion during Jump Assist.
