Bulletin No.:

Service Bulletin

Date:

23-NA-189
October, 2023

INFORMATION
Subject:

Information on Setting Up PicoScope to Diagnose Controller Area Network (CAN)
Circuits

Brand:

Model:

BrightDrop

All
Passenger
Cars and
Light/
Medium
Duty Trucks
and SUVs

Buick
Cadillac
Chevrolet
GMC

Model Year:

VIN:

from

to

from

to

2020

2024

—

—

Involved Region or Country

Transmission:

—

—

North America, Argentina, Brazil, Bolivia, Chile, Colombia, Ecuador, Paraguay, Peru,
Uruguay, Venezuela, Europe, Uzbekistan, Russia, Middle East, Iraq, Israel, Palestine,
Japan, Cadillac Korea (South Korea), GM Korea Company, China, Taiwan, Thailand,
Singapore, Philippines, Australia/New Zealand, Egypt, Other Africa, South Africa

Service Procedure
Important: Service agents must comply with all
International, Federal, State, Provincial, and/or
Local laws applicable to the activities it performs
under this bulletin, including but not limited to
handling, deploying, preparing, classifying,
packaging, marking, labeling, and shipping
dangerous goods. In the event of a conflict between
the procedures set forth in this bulletin and the
laws that apply to your dealership, you must follow
those applicable laws.
Important: This technical service bulletin (TSB) can
only be completed by certified repair facilities who have
met all specific training, tool and equipment
requirements pertaining to the vehicle Brand and Model
serviced. Repairs must be performed by a technician
who has successfully completed the required training.
Important: The data link connector (DLC) can only
be used to monitor controller area network (CAN)
bus voltages on vehicles without a Serial Data
Gateway Module (SDGM). On vehicles with a SDGM,
the CAN bus voltages must be checked at a module
or in-line connector on the network.

Copyright 2023 General Motors LLC. All Rights Reserved.

Engine:

This bulletin is designed to assist technicians in setting
up the PicoScope hardware and software to monitor
CAN bus traffic (voltage patterns) to aid Technical
Assistance (TAC) and Field Service Engineers (FSEs)
in diagnosing electrical issues present on network
communication circuits. You must have GM Special
Tools CH-51450-B as well as CH-51450-LEAD-A in
order to follow the steps listed below.

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October, 2023

Prior to following the steps listed below, you must run a
vehicle-wide DTC check. Verify that there are U-codes,
either current, or in history, and use the appropriate
Service Information (SI) documents to verify which
CAN bus the issue is likely to be on. Once you have
determined the CAN bus that the fault is likely present
on, carefully follow the steps listed below for your
vehicle:
Important: Backprobing sealed connectors is not a
GM-approved test method.
1. On your dealer computer, open the PicoScope 7
software. The icon looks like this:

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2. Ensure your PicoScope is plugged into your
computer and is selected:

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Bulletin No.: 23-NA-189

3. Locate the channel settings (1) on the left side of
the PicoScope screen, and ensure that channels A
and B are set to +/- 10 V.
– Clicking in the “A” channel box will bring up the
voltage options for that channel. You can also
adjust the voltage settings by using the “+” or “-“
buttons located on the left and right side of each
channel.

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4. Locate the “Time base” settings (2) and ensure that
it is set to 100 ms/div or less.

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– Under the “Time base” settings, locate the
“sampling” button, and ensure that the Target
Sampling Rate is 10 MS/s.
5. Hook up the PicoScope leads to the CAN bus you
previously identified as the one experiencing the
concern. (Reference Doc ID# 2414974 for proper
electrical probing techniques and procedures that
are supported by GM.)
• Use the appropriate wiring diagram and ensure
that one lead is attached to the CAN + circuit
and the other to the CAN – circuit.
• The black lead of each PicoScope Electrical
lead will be attached to a known good ground.
6. Operate the vehicle in the conditions under which
the customer’s concern can be duplicated, while
allowing the PicoScope software to run. Once the
concern has been duplicated, stop the PicoScope
recording and save the file.

Bulletin No.: 23-NA-189

Bulletin No.: 23-NA-189

October, 2023

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6.A.
Clicking the “Stopped” or “Running” (3) button in
the top-left corner of the screen will either stop
or start the recording. The spacebar can be
used as a shortcut to stop or start the recording
as well.
6.B.
If the recording is STOPPED, and you start the
recording again, all previously recorded
waveforms will be deleted. It is crucial that you
use the next steps to save your recording
before starting a new recording.

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7. Select the “Save” button (4) in the upper-middle of
the screen.
7.A.
In the popup after clicking to save the file,
locate the “Channel Labels” button and label
the channels. Include circuit numbers, pins, and
connector numbers.

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Bulletin No.: 23-NA-189

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7.B.
Input all vehicle specific information (5),
channel labels and notes (6) about when the
concern was present, and if the concern was
present while the PicoScope was hooked up
and running.
7.C.
Click the “Save” button in the bottom-left of the
popup window.
8. To upload the PicoScope file to your TAC case,
locate your TAC case in the Dealer Case
Management system, and once opened, select the
“Add Attachment” tab in the Dealer Case
Management tool.

Version

1

Modified

Released October 25, 2023

8.A.
Once you have clicked the “Add Attachment”
button, locate the file on your computer, and
select it. The file will now be loaded into the
“Edit attachment” box. At this point, please add
any comments that are needed, and then select
the “Save” button at the bottom of the “Edit
Attachment” box. This will save your file to the
TAC case.
8.B.
Bulletin # PIP4902R can be referenced for
pictures or assistance with uploading the file to
the TAC case.
TAC review and response times may vary based on
volume of cases. Your patience is appreciated during
their review.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

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