• Control the system from the front Infotainment
Screen (turn the screens on/off, listen in on what’s
currently playing, lock the system and more)

Bulletin No.: 20-NA-211

Rear Seat Entertainment
System Components
The available rear seat infotainment system includes:
1. two seat headrest display screens
2. rear consumer port
3. up to 4 pairs of wireless headphones
System Operation
Display 1 is a smart device and is connected to the
radio via Ethernet. Display 1 is connected to Display 2
and the rear consumer port via a low-voltage differential
signal cable. The radio controls each display with a
remote enable circuit. The rear seat infotainment
system is entirely controlled by touch screen inputs.
There are no remote controls or external buttons.
To turn the rear seat infotainment system ON, touch
anywhere on the desired display and the home screen
will display. The home screen is divided into a bottom
status bar and three control panels. The bottom status
bar provides the home button, current time, access to
system settings, Bluetooth® headphones settings, and
a power button to turn OFF the associated screen. USB
devices can be used for audio and video. Bluetooth®
HDMI devices can be paired to the system and smart
phones can be paired as media devices.
Display Screens

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Display 1 is located at the rear of the passenger seat.
Display 1 is a programmable display and is connected
to the radio via Ethernet.
Display 2 is located at rear of the driver’s seat. Display
2 is non programmable and only displays the signal
communicated from Display 1 via a low-voltage
differential signal cable.
The rear displays utilize a 32cm (12.6-in) fixed 16×9
aspect ratio, touch screen LCD with 1920×1080 pixel
resolution. The factory default/power reset for both
displays is OFF (including audio).

Bulletin No.: 20-NA-211

October, 2020

Rear Consumer Port
The rear consumer port connects to Display 1 via a
low-voltage differential signal cable. The rear consumer
port includes the following inputs:
• USB (audio and video)
• HDMI 1
• HDMI 2
• Miracast
USB
Along with the USB port in the rear consumer port, any
USB port in the vehicle can provide USB content for the
rear seat infotainment system. The USB devices are for
audio and video.
HDMI
The HDMI input allows an HDMI audio/video cable
connection from an auxiliary device, such as a
camcorder or video game system. For certain HDMI
devices supporting USB charging, the USB ports can
provide power to the source.
Miracast
Note: Apple does not support the Miracast standard.
The rear seat infotainment system Wi-Fi supports
Miracast to display smart devices directly on the rear
seat infotainment screens. Miracast only supports one
device at a time. The smart device must support
Miracast, screen mirroring, or Android Wireless Display.
Wireless Headphones
The rear seat infotainment system includes two or four
pairs of 2-channel digital wireless headphones.
Wireless headphones allow for rear seat passengers to
listen to an audio source without disturbing front seat
passengers. The wireless headphones receive audio
signals from the infrared transmitter located on the top
of the left seatback display.
A power button on the headphones turns them off or
on. A red Light Emitting Diode (LED) illuminates when
the headphones are ON. The headphones
automatically turn OFF if the infrared signal from the
system is lost for approximately 4 minutes to preserve
battery life. The signal may be lost if the system is
turned off or the infrared signal is out-of-range of the
transmitters.
Each set of headphones has a rotary volume control on
one of the earpieces.
Audio to the wireless headphones is provided over 2
channels. Audio for channel 1 or channel 2 is selected
by pressing the button in the center of the headphone
volume control.
The system supports Bluetooth® headphones. Up to 9
pairs of Bluetooth® headphones can be paired to each
rear display.

Secure Digital Card Reader, USB Port, and
Auxiliary Audio Input Jack
A secure digital card reader, a USB port(s), and/or an
auxiliary audio input jack may be part of an assembly
for use by the infotainment system. Located in the
center console, the assembly receives fused battery
voltage and ground from the vehicle harness. The

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vehicle harness provides power to a hub device integral
to the assembly and provides additional amperage to
allow the USB port to power devices.
The internal hub device interfaces directly with the
remote radio receiver via a standard USB cable. An
inline cable connection is typically found between the
console and instrument panel harness.
Secure Digital Card Reader
On vehicles equipped with navigation, the secure
digital card will contain the map information for the
vehicle region.
USB Port
Note: Not all portable media player devices or file
types are compatible. Connection to USB hub devices
is not supported.
The USB port allows the user to send information to the
infotainment system from portable media players or a
USB storage device. When a device is connected to the
USB port, it can be controlled from the radio controls.
Auxiliary Audio Input Jack
A 3.5mm (1/8-in) auxiliary audio input jack is located in
the center console. When a portable audio playback
device is connected to the auxiliary jack, an internal
switch detects the connection. The radio will then
switch to the auxiliary audio input jack as the audio
source. The device sends audio signals to the radio
from the auxiliary jack via USB.
Auxiliary Power Outlets
Accessory power outlets for electrical equipment, such
as a cell phones or MP3 players, are located under the
climate control system.
The vehicle is equipped with a 110/230 volt Alternating
Current (AC) outlet on the rear of the center console
and the cargo area for third row seating. Lift the cover
to access the outlets and close the cover when not in
use. In regions outside of the USA, the AC outlets are
available in 230 volts.
Operation
The accessory DC/AC power inverter module receives
fuse protected battery voltage. The 110/230 volt
accessory power receptacle has an internal switch that
detects when an AC powered device is plugged into the
outlet. The accessory AC power system is protected
against circuit overload and circuit shorts to ground.
Power Outlet Receptacle Isolation Fault Protection
In addition, the power inverter module contains a
ground fault circuit interrupter. The ground fault circuit
interrupter monitors the 110/230 volt circuit for a short
to vehicle chassis ground. If a short to ground is
detected, the accessory DC/AC power inverter module
turns OFF. The module remains OFF until the AC
powered device is disconnected from the outlet and
then plugged into the outlet after a 3 second delay.

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October, 2020

Power Outlet Receptacle Overload Shutdown

Bulletin No.: 20-NA-211

In a mid/high radio system configuration without a
telematics control module and equipped with GPS, the
radio provides the GPS and heading information on low
speed Info-CAN.
An external remote compass module is required to
transmit the heading and position information on low
speed Info-CAN if either:
• the base radio is present in a system configuration
with no telematics communication interface
control module
• the radio variant without GPS is present in a
system configuration with no telematics
communication interface control module

Power and Signal Distribution

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The accessory DC/AC power inverter module turn OFF
if the current in the 110/230 volt outlet (shown circled
above) is greater than 3.8 amps for 1 second or 2.5
amps for 10 seconds. The module turns ON when the
AC powered device is disconnected from the outlet and
then plugged into the outlet after a 3 second delay.

OnStar®
When OnStar® is activated, a serial data message is
sent to the audio system to mute all radio functions and
transmit OnStar® originated audio. The OnStar® audio
is transmitted to the vehicle audio system by the
Ethernet circuit. When the audio source is OnStar®, the
fade is set to the front, the bass and treble are set to the
middle, and the outputs are mono. OnStar® takes
priority over any other audio source. On vehicles
equipped with OnStar®, the HVAC blower speed may
be reduced when the OnStar® system is active to aid in
reducing interior noise. When the system is no longer
active, the blower speed will return to its previous
setting.
OnStar® Cellular, GPS, and Diagnostic Limitations
Proper operation of the OnStar® System is dependent
on several elements outside the components integrated
into the vehicle. These include the National Cellular
Network Infrastructure, the cellular telephone carriers
within the network, and the GPS. The cellular operation
of the OnStar® system may be inhibited by factors such
as the user’s range from an analog or digital cellular
tower, the state of the cellular carrier’s equipment, and
the location where the call is placed.

Compass Data
With the base radio, the telematics communication
interface control module provides compass and GPS
position information on the low speed Info-CAN bus.

Overview
The 2021 Cadillac Escalade is designed and
engineered with GM’s Vehicle Intelligence Platform
(VIP). This advanced data communication platform
enables key benefits, including increased system
capacity and responsiveness, increased over-the-air
vehicle software update capability, and enhanced
cybersecurity.

GM’s Vehicle Intelligence Platform (VIP)
GM’s next generation digital vehicle platform enables
increased capacity and the ability to better manage
technology complexity. Next generation networks
include two-wire CAN buses and two-wire Ethernet
buses to ensure high speed data transfer and multiple
single-wire LIN buses to exchange information between
master control modules and other smart devices. Low
speed General Motors Local Area Network (GMLAN)
networks are eliminated.
Key benefits of next generation electrical architecture
include:
• increased system capacity and responsiveness,
including the capability of managing over 100
computer modules seamlessly and delivering up
to 4.5 terabytes of data processing power per hour
• increased over-the-air vehicle software update
capability, including over-the-air software updates
(without dealer visits)
• enhanced cybersecurity, with additional system
encryption, higher-level security routines, and
additional protective features at both hardware
and software levels

Controller Area Network Buses
Next generation electrical architecture communication
protocol is based on the widely used CAN protocol.
CAN buses are used where data needs to be
exchanged at a high rate, primarily by a control device
using the information to adjust a vehicle system, such
as powertrain or body controls.
Each CAN data network consists of two twisted wires,
called CAN (+) and CAN (-), with a 120 ohm (Ω)
termination resistor at each end of the bus between the
CAN (+) and CAN (-) circuits.

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October, 2020

Data Transmission
Data transmitted is represented by the voltage
difference between the CAN (+) and CAN (-) signals.
Logic symbols (1’s and 0’s) are transmitted sequentially
at the following rates:
• CAN 1 = 500 Kilobits per second (Kbit/s)
• CAN 2 = 2 Megabits per second (Mbit/s)
• CAN 3 = 500 Kbit/s
• CAN 4 = 500 Kbit/s
• CAN 5 = 500 Kbit/s
• CAN 6 = 5 Mbit/s
• CAN 7 = 5 Mbit/s
• CAN 8 = 2 Mbit/s
• CAN 9 = 2 Mbit/s
• Private Powertrain CAN Bus
A logic “1” is transmitted when both CAN (+) and CAN
(-) signal circuits are at rest and at the same voltage of
2.5 V. The differential voltage is approximately 0 V.
A logic “0” is transmitted when the CAN (+) signal
circuit is driven higher to about 3.5 V and the CAN (-)
circuit is driven lower to about 1.5 V. The differential
voltage then becomes approximately 2.0 (+/- 0.5) V.

Ethernet Buses
Ethernet is a data communication technology that uses
a single twisted copper pair of wires at speeds of 100
Mbit/s and 1000 Mbit/s. The Ethernet system uses
point-to-point communication that is connected via an
Ethernet switch [Module Switch Module]. The
Ethernet bus does not use terminating resistors. The
Cadillac Escalades incorporate an Ethernet audio video
bridging bus in place of a Media Oriented Systems
Transport (MOST®) network.
The K56 serial data gateway module and the A11 radio
have an Ethernet switch that connects to other Ethernet
modules. The K56 serial data gateway module and the
A11 radio communicate with other devices and systems
in the vehicle via CAN and LIN buses. DTCs will be
read on CAN to diagnose Ethernet, LIN, and system
faults.
Note: Ethernet harness failures should only be
repaired using an appropriate kit to perform de-pin/
re-pin overlays; in cases where the wiring harness
repair kits are not available, the entire harness should
be replaced. No crimps or splicing should be performed
on the Ethernet wiring harness.
Ethernet 1
The Ethernet bus 1 consists of two twisted pairs of
wires—one pair for Ethernet bus 1R (circuits 4972 and
4973) and one pair for Ethernet bus 1T (circuits 4974
and 4975). It is connected between the X84 DLC and
K56 serial data gateway module. This bus is used for
diagnostics and service programming of control
modules using Ethernet instead of CAN. The K56 serial
data gateway module will convert Ethernet serial data
to CAN as necessary, and vice versa. There is an
Ethernet enable circuit (circuit 7207), which can be
used to wake up the K56 serial data gateway module
for Ethernet diagnostics and programming.

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Ethernet 2
Ethernet bus 2 (circuits 4757 and 4758) is for
connection between the A11 Radio and the K56 serial
data gateway module.
Ethernet 3
Ethernet bus 3 (circuits 7208 and 7209) is for
connection between the K56 serial data gateway
module and the K179 automated driving mapping
module.
Ethernet 4
Ethernet bus 4 (circuits 7210 and 7211) is for
connection between the following control modules:
• K56 serial data gateway module and K73
communication interface module for vehicles
equipped with IOR radio
• A11 Radio and K73 communication interface
module for vehicles equipped with other radios
Ethernet 5
Ethernet bus 5 (circuits 7212 and 7213) is for
connection between the A11 radio and the P22F video
display - passenger seat back.
Ethernet 6
Ethernet bus 6 (circuits 7214 and 7215) is for
connection between the A11 radio and the T3 audio
amplifier.
Ethernet 7
Ethernet bus 7 (circuits 7216 and 7217) is for
connection between the K56 serial data gateway
module and the P16 instrument panel cluster control
module.
Ethernet 11
Ethernet bus 11 (circuits 7224 and 7225) is for
connection between the K124 image processing
module and K179 the automated driving mapping
module.
Ethernet 14
Ethernet bus 14 (circuits 7230 and 7231) is for
connection between the A11 radio and the P29 head-up
display.
Ethernet 15
Ethernet bus 15 (circuits 7232 and 7233) is for
connection among the K56 serial data gateway module,
K161 vehicle performance data recorder, and P22F
video display - passenger seat back.

Local Interconnect Network Buses
LIN buses are single-wire buses that exchange
information between the master control module and
subordinate smart devices. LIN buses communicate at
a rate of up to 10.417 Kbit/s. The K9 body control
module is wired to multiple LIN buses and acts as a
gateway between them.

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October, 2020

Local Interconnect Network Bus Data Transmission
Data transmitted is represented by voltage difference
expressed in logic symbols (1s and 0s) and transmitted
sequentially:
• When a LIN bus is at rest and is not being driven,
the signal high voltage state is approximately
battery voltage. This represents a logic “1”.
• When a logic “0” is transmitted, the signal voltage
is low to about ground (0.0 V).
K9 Body Control Module
The K9 BCM communicates through multiple
communication buses to control the vehicle’s body
systems. The BCM is wired to the CAN 2 serial data
bus and multiple LIN buses and acts as a gateway
between them. Some inputs, outputs, and messages
require other modules to interact with the BCM. The
BCM is located in the passenger compartment, behind
the driver side of the instrument panel, outboard of the
steering column.

K56 Serial Data Gateway Module
The K56 serial data gateway module handles
communication between multiple buses and control
modules, as well as buses and the X84 data link
connector.
• CAN 1, CAN 2, CAN 3, CAN 4, CAN 5, and CAN 8
buses are used to communicate between the K56
serial data gateway module and other CAN control
modules.
• CAN 6 and CAN 7 buses are used to communicate
between the X84 Data Link Connector and the
K56 serial data gateway module. They are also
use for diagnostics, and programming.
• The Ethernet AVB bus is used to connect the radio
and K56 serial data gateway module.
Cyber Security
The K56 serial data gateway module also functions as
a gateway to isolate the secure networks from the
unsecured networks.
Isolating secure networks from unsecured networks
supports cyber security. Isolating primary networks
helps ensure advanced driver assistance systems and
active safety features, such as enhanced collision
avoidance, can all operate in conjunction with each
other. If harmful software enters the vehicle through the
infotainment system, OnStar®, or the DLC, other
vehicle systems may be affected, including critical
powertrain and safety systems.
The serial data gateway module can learn the
diagnostic addresses list of CAN control modules,
identify the CAN control modules on the vehicle, and
the location of the CAN control modules’ CAN buses. If
the serial data gateway module is replaced, this learn/
verification process must be performed again through
the Serial Data Gateway Module Programming and
Setup procedure in Service Programming System
(SPS). The learn process does not cause any
previously learned contents to be forgotten or
overwritten. If the learn process is not performed on a
new serial data gateway module, DTC U1977 sets until
the learn procedure is executed. If the learn is invalid

Bulletin No.: 20-NA-211

due to control module internal malfunction or a serial
data gateway module swap, DTC U3000 42 or DTC
U3002 56 sets. If these DTCs set, the serial data
gateway module enables a loss of communication for
all CAN control modules. This results in loss of
communication DTCs set against CAN control modules
not present on the vehicle.
A malfunction can be localized by monitoring the
normal mode messages on a CAN bus. The serial data
gateway module monitors one signal per CAN control
module per CAN bus to determine control module
status. When a signal times out, a loss of
communication event will be started.

Power Moding
In next generation electrical architecture, the K9 BCM is
the Power Mode Master (PMM) and the K56 serial data
gateway module is the back-up PMM.
There are five power modes:
• OFF
• ACCY
• RUN/SERVICE MODE (Engine Off)
• PROPULSION (Engine On)
• Start
As the PMM, the BCM uses a number of vehicle states
and inputs to determine which power mode is required.
It then reports this information to other modules via
serial data and provides associated electrical signals to
the entire vehicle to ensure proper feature operation.
The backup PMM, the K56 serial data gateway module,
is responsible for determining and sending a system
backup power mode serial data signal along with the
other related signals to downstream features when the
power mode master is unavailable.
Modules with switched voltage inputs may operate in a
default mode if the power mode serial data message
does not match what the individual module can see
from its own connections.
Automatic Power Mode Timeouts
Automatic power mode timeouts prevent batteries from
losing charge if the ignition is left on (RUN/SERVICE
MODE – Engine Off) while the vehicle is unattended,
and the timeouts also shut the vehicle off if it is left
running unattended (PROPULSION – Engine On). After
a timeout, the BCM power mode master shuts the
engine down. This power mode timeout strategy uses
vehicle speed, vehicle power mode, parked status, and
other vehicle conditions to determine the timeout. Refer
to Service Information (SI) for power mode description
and operation.

System Diagnostics
K56 Serial Data Gateway Learn Process
To signal any loss of communication and set DTCs, the
K56 serial data gateway module must know and learn
the control modules on the vehicle and their associated
buses.

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October, 2020

If the K56 serial data gateway module is replaced or
another module is added to the bus, such as a dealer
installed accessary, a learn process must be done
using the serial data gateway module learn procedure
in SPS.
The serial data gateway learn process may be
performed by a technician or automatically sequenced
as part of a control module programming event.
• Technician selectable option: The learn process
may be performed by a technician when a DTC is
present, with no control module programming
required.
• Automatically sequenced as part of a control
module programming event: The learn process
may be automatically sequenced after
programming a module.
The learn process will not cause any previously learned
contents to be forgotten or overwritten.
• If the learn process is not completed on a new K56
serial data gateway module, DTC U1977 will be
set until the learn procedure is executed.
• If the learn process is invalid due to internal
malfunction or a K56 serial data gateway module
swap, DTC U3000 42 or DTC U3002 56 will be
set. The K56 serial data gateway module will then
lose communication with all control modules and
set DTCs against control modules not on the
vehicle.
A fault can be localized by monitoring the normal mode
messages on a CAN bus. The K56 module will monitor
one signal per CAN control module per CAN bus to
determine control module status. When a signal times
out, a loss of communication DTC sets. The K56 serial
data gateway module will create a freeze frame for U
codes.
Module Programming
Refer to the Techline Information System (TIS) terminal
for step-by-step control module programming
instructions and review the information below to ensure
proper programming protocol:
• The key must be OFF during module programming
and all doors closed. If a door is opened during
programming, other buses will wake up and cause
error codes to set.
• DO NOT change the position of the ignition switch
during the programming procedure unless
instructed to do so.
• Options need not be selected during SPS
programming.

Odometer Strategy
With next generation electrical architecture, the
odometer value is stored in multiple modules. The BCM
is the primary storage module and accumulator of
vehicle mileage data. The instrument panel cluster
control module is a secondary storage module. There is
no provision for entering odometer information from any
external source such as SPS programming. Any
odometer information required for an odometer learning
procedure must come from vehicle modules. The

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automated process removes any need for technician
input and keeps all stored odometer values
synchronized.

Over-the-Air Updates
The next generation digital vehicle platform enables
over-the-air programming for all control modules with