Bulletin No.: 21-NA-141

July, 2021

Page 7

The Hybrid/EV Powertrain Control Module 1 is the host
controller for DTC information for the Drive Motor
Control Module.
The Drive Motor Control Module and the Hybrid/EV
Powertrain Control Module 1 exchange information and
commands on a serial peripheral interface bus internal
communication circuit, as well as the Powertrain
Expansion Bus.
Hybrid/EV Powertrain Control Module 2
The Hybrid/EV Control Module 2 located inside the
cabin, performs a number of functions:
• Processes information sent from the Battery
Energy Control Module to learn the battery
capacity, battery state of charge, and thousands of
parameters behind the scenes as the hybrid/EV
battery pack is discharged and charged.
• Determines the speed of the hybrid/EV electronics
coolant pump.
• Controls the radiator fans.
• The Engine Control Module (ECM) sends the
cooling fan command to the Hybrid/EV
Powertrain Control Module 2, and the Hybrid/
EV Powertrain Control Module 2 sends the
signal to the cooling fans to operate and at
what speed.
• If the vehicle is in Charge Mode, the Hybrid/EV
Powertrain Control Module 2 controls the
cooling fans without ECM intervention.
• Measures a high impedance network within the
T24 battery charger - DC to verify isolation
between the DC high voltage positive and
negative circuits and the vehicle chassis is within
the proper range.
• Sends the signal for the high voltage interlock
circuit.
Battery Energy Control Module
The BECM is internal to the high voltage battery. The
BECM collects temperature information from six
sensors mounted to specific battery modules, as well
as voltage from each cell group, through volt sense
wires and total system current. The BECM sends this
information to the Hybrid/EV Powertrain Control Module
2 for processing.
Caution: BECM Replacement requires a specific
sequence to disconnect and reconnect in order to
prevent internal damage due to voltage spikes. Refer to
SI for additional details.

5867229

Accessory DC Power Control Module
The Accessory DC Power Control Module is an
electronic device that takes the place of the generator
on a traditional vehicle. The Accessory DC Power
Control Module is located in the front compartment atop
the on-board charger. The Accessory DC Power
Control is also known as the 14-V power module and
converts high voltage (350 volts DC) to low voltage
(approximately 14 volts DC) for accessory electrical
operation, as well as to charge the 12-volt battery. The
module has no internal diagnostic tests and does not
communicate over serial data. The ECM monitors and
controls the 14-volt power module and will report DTCs
if a fault is detected.
Normally, the Accessory DC Power Control Module
supplies approximately 14-volts DC when the vehicle is
under a normal drive cycle. However, there are certain
instances when the vehicle is charging and Accessory
DC Power Control Module operation is required to
charge the 12-volt battery. The module is capable of
supplying up to 1.6 kilowatts (kW) at 165 amps of 12
volts DC.

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July, 2021

Bulletin No.: 21-NA-141

4. A/C Compressor Cables
5. Drive Motor/Generator Power Inverter Module
Cables
6. Cabin Heater Cables
7. Main Cables from Battery
8. Three-Phase Cables

High Voltage Cables

5867230

High Voltage Distribution
The generator battery control wiring junction block is
essentially an electrical distribution block, allowing all
high voltage components to connect directly to the high
voltage DC system. The 400-amp fuse within the
manual service disconnect protects the cables from
shorts. Within the block there are bus bars that
distribute the high voltage to the Drive Motor/Generator
Power Inverter Module connector as well as the A/C
compressor, Cabin Heater Control Module, on-board
charger, battery heater, and the DC charger positive
and negative cable contactors, if equipped. The A/C
compressor and the cabin heater are protected from
shorts using non-serviceable 30 amp fuses internal to
the block.

High voltage current transfers between components
through high voltage DC cables or three-phase AC
cables. The high voltage cables do not utilize the
vehicle chassis as the ground path; instead, both
positive and negative high voltage cables connect the
components. Each individually shielded cable is orange
in color to alert the technician to the potential presence
of high voltage.
The high voltage cables are isolated from the vehicle
chassis by a specific amount of resistance and are
individually shielded to reduce electromagnetic
interference. Cable connections at the high voltage
components must be torqued properly to ensure proper
electrical contact. A loose high voltage electrical
connection may cause microscopic pitting of the
contacts, which increases resistance and may result in
system faults.

5867232

Three-Phase AC Cables

5867231

High Voltage Distribution
1. Charger Cables to Battery
2. Battery Heater Cables
3. On-Board Charger Cables

Three individual cables connect each phase of the
drive motor to the Power Inverter Module. Similar to the
high voltage cables, each individually shielded
three-phase AC cable is orange in color to alert the
technician to the potential presence of high voltage.
Again, it is critical that high voltage component
connections are torqued properly to ensure proper
electrical contact. A loose high voltage electrical
connection may cause microscopic pitting of the
contacts, which increases resistance and may result in
system faults.

Bulletin No.: 21-NA-141

July, 2021

5867233

Drive Motor Battery Thermal Management
System
Drive motor battery thermal management is essential
for electric vehicles, as the battery is very sensitive to
temperature. The system uses conduction through a
cooling fin to draw the heat down below the cells and
into coolant circulating through coolant plates.
These plates also serve as the cell section support
structure. Additionally, there are thermal pads between
the sections and the coolant plate that help to evenly
distribute the temperatures of the cells and minimize
thermal shock. The system does not use a radiator to
transfer the heat to the air.
Under most operating conditions, the system is capable
of dissipating enough heat simply by circulating the
coolant. If temperatures get too high, the A/C system
will activate and remove heat through a cooler.
The drive motor battery cooling system circulates
pre-mixed DEX-COOL®, which is a 50/50 mixture of
DEX-COOL® and de-ionized water. De-ionized water is
required for high voltage isolation and to prevent
corrosion from affecting heat sink performance.
Caution: Always use pre-mixed coolant and never use
tap water in the battery coolant system.
The drive motor battery cooling system may activate
when the vehicle is operating, during charging, or when
the vehicle is off and maintaining the drive motor
battery temperature.

Page 9

5867234

Drive Motor Battery Thermal Management System
1. Drive Motor Battery Coolant Cooler
2. Surge Tank
3. A/C Compressor
4. Coolant Pump
5. Battery Heater

Battery Heater
The 1.8 kW heater, which is external to the battery
assembly, preheats the battery in cold conditions for
optimal performance.
The Hybrid/EV Powertrain Control Module 2 monitors
the battery cell temperature and turns on the high
voltage heater when necessary. The heater uses a high
voltage heater coil to heat the coolant as it passes
through the heater, just before it enters the battery
assembly.
The heater is commonly used in colder climates to
preheat the battery prior to propulsion or charging.
Since battery cell operation and charging create heat,
the heater is typically only needed for a brief period
of time.

Page 10

July, 2021

Bulletin No.: 21-NA-141

The power electronics cooling system circulates a
pre-mixed DEX-COOL® which is a 50/50 mixture of
DEX-COOL® and de-ionized water. De-ionized water is
required for high voltage isolation and to prevent
corrosion from affecting heat sink performance.
Caution: Always use pre-mixed coolant and never use
tap water in the battery coolant system.

5867235

Drive Motor Battery Coolant Cooler
The drive motor battery coolant cooler, located in the
front mounted to the right strut tower, uses the vehicle's
A/C system to cool the high voltage battery coolant to
maintain proper temperature.
As the A/C system operates, refrigerant passes through
a thermal expansion valve on the coolant cooler. The
refrigerant drops in temperature to draw heat out of the
high voltage battery coolant and cool the battery cells.
The coolant cooler is a fluid-to-fluid heat exchanger
with its own thermal expansion valve.

5867237

The Hybrid/EV Powertrain Control Module 2 activates
the coolant pump and monitors the coolant temperature
sensor in the radiator. The coolant pump will activate
when the vehicle is ON and during charging. The
coolant pump and radiator cooling fans may activate
when the vehicle is OFF, depending on coolant
temperature.

Charging System

5867236

Power Electronics Cooling System
The primary purpose of the hybrid power electronics
cooling system is to cool the T6 Power Inverter Module,
T18 battery charger, K1 14V Power Module, and the
transmission. The power electronics cooling system
uses a radiator, control module inputs, a radiator fan,
and the coolant pump to circulate coolant through the
system.

The high voltage battery charging system consists of
the following main components:
• drive motor battery charger cord set, often referred
to as electric vehicle supply equipment.
• dual-mode charge cord:
• often referred to as a dual level charge cord.
• capable of charging at the electric vehicle
supply equipment rate of 12 amps from the 120
volt outlet.
• capable of charging at a rate of 32 Amps from
a 240 volt outlet.
• drive motor battery charger cord receptacle, often
referred to as the charge port.
• T18 drive motor battery charger, often referred to
as the onboard charger module which converts
grid AC into DC to charge the battery pack.
• T24 Battery Charger - DC
• drive motor battery, sometimes referred to as the
high voltage battery.

Bulletin No.: 21-NA-141

July, 2021
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Page 11
Do not use extension cords, multi-outlet power
strips, splitters, grounding adapters, surge
protectors, or similar devices.
When outdoors, plug into an electrical outlet that is
weatherproof.
Mount the charge cord to reduce strain on the
electrical outlet/plug.
Do not place the charge cord anywhere it could be
submerged in water.

5867238

Standard for Bolt EUV, Optional on Bolt EV:
Dual Mode Drive Motor Battery Charger Cord,
RPO EKT
The drive motor battery charger cable provided with the
Bolt EUV features a new swappable 120V standard
household electrical plug or a 240V NEMA 1450
electrical plug. The other end is designed to plug into
the vehicle’s charge receptacle. The dual mode
portable charger can be used for level 1 and level 2
charging. This charger features a charge current
interrupt device with AC power and fault indicators and
is stored in the vehicle’s cargo area.

Bolt EV: Standard Level 1 Drive Motor Battery
Charger Cord
This cord set is the same as the current 2021 Bolt EV
and is capable of plugging into a standard 120V
household electrical plug. Charge rates are limited to 8
amps unless location based charging is applied which
then allows charging rates up to 12 amps.

Circuit Interrupt Device
Each cord set includes an integrated charge circuit
interrupt device that stops the flow of AC current until
the cord is properly mated with a vehicle and
self-checks have completed successfully. The charge
circuit interrupt device will also cut the current flow if
faults occur during the charge event.
Portable Electric Cord Charging Considerations
• Charging an electric vehicle can stress a
building’s electrical system more than a typical
household appliance.
• Before plugging into any electrical outlet, a
qualified electrician should inspect and verify the
electrical system (electrical outlet, wiring,
junctions, and protection devices) for heavy-duty
service at a 12-amp continuous load for level 1
charging and 32 amp load for continuous level 2
charging.

5867239

Battery Charger Cord Status Indicators
Both standard and dual mode drive motor battery
charger cable contains LEDs that indicate the status of
the drive motor battery charger cable. The cable
automatically prevents charging if it senses internal
faults or inadequate household voltage. The status
lights can alert the user of faults as described in the
tables below.

Level 1 Portable Charger: Standard ONLY
on Bolt EV
Single Mode (Voltage) Charge Cord Status
Indicator Key
Indicator

Indicator

Condition

Solid Green

Off (No Light)

Ready to
Charge

Flashing
Green

Solid Red

Household
Electrical
Outlet/ AC
Plug
Overheated

Off (No
Light)

Solid Red

System Not
Properly
Grounded

Off (No
Light)

Flashing Red

Vehicle Fault
Detected

Solid Green

Flashing Red

Charge Cord
Fault
Detected

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July, 2021

Bulletin No.: 21-NA-141

Dual Mode Portable Charger: Optional on
EV, Standard on EUV
Dual Mode (Voltage) Charge Cord Status Indicator Key
Indicator

Indicator

Indicator

Condition

Off
(No Light)

Solid Blue

Off
(No Light)

Ready to Charge

Off
(No Light)

Pulsing Blue

Off
(No Light)

Charge in
Progress

Off
(No Light)

Charging at
reduced rate due
to high
temperature of
plug or
charge cord

Off
(No Light)

Charging at
reduced rate due
to high
temperature of
plug or household
electrical outlet

Off (No Light)

Solid Red

Charge Cord
Internal Fault
Present

Off (No Light)

Off
(No Light)

Swappable Plug
Not Fully Seated,
Household
Electrical Outlet
Fault

Amber

Off (No Light)

Off
(No Light)

Overtemperature
of AC plug,
swappable plug or
charge cord
internal module

Solid
Amber

Solid Blue

Solid Red

Charge Cord
Reset In Progress

Solid
Amber

Single
Flash —
Amber

Off
(No Light)

Amber

Pulsing Blue