21NA139

Service Bulletin
Bulletin No.:
21-NA-139
Date:
June, 2021
TECHNICAL
Subject:
Brand:
Buick
Cadillac
Chevrolet
GMC
Holden
Malfunction Indicator Lamp (MIL) Illuminated – DTC P3055 Set
Model:
Model Year:
VIN:
from
to
Enclave
2017
2021
LaCrosse
2017
2020
Regal
2018
2021
CT6
2017
2019
XT4
2019
2021
XT5
2018
2021
XT6
2020
2021
Blazer
2019
2021
Cruze
2017
2021
Equinox
2018
2021
Malibu
2017
2021
Silverado
1500 (New
Model)
2019
2019
Silverado
1500
2020
2021
Traverse
2018
2021
Acadia
2018
2021
Sierra 1500
(New Model)
2019
2019
Sierra 1500
2020
2021
Terrain
2018
2021
Acadia
2019
2020
from
to
—
—
Engine:
Transmission:
—
—
Involved Region or Country
North America, Brazil, Middle East, China, Australia/New Zealand
Additional Options (RPO)
Equipped with Stop/Start (RPO KL9)
Condition
Some customers may comment that the Stop/Start function is inoperative, and the MIL is
illuminated.
Some technicians may find DTC P3055 (DC/DC Converter Output Voltage 1
Performance) set in the Engine Control Module (ECM).
Cause
This concern may be caused by the DC/DC Module being mis-configured and Channel 1
doesn't boost properly.
Copyright 2021 General Motors LLC. All Rights Reserved.
Page 2
June, 2021
Bulletin No.: 21-NA-139
Refer to Document ID# 4773341: Circuit/System Verification/Testing.
Verify a test lamp does not turn on between terminal 10 and ground:
• If the test lamp turns on, repair the short to voltage on circuit 2172.
• If the test lamp does not turn on, remove all appropriate fuses supplied by circuit 2172.
Test for infinite resistance between Terminal 10 at the T19 Power Supply Transformer and
ground:
Note: A less than infinite reading can be caused by component circuits being shorted to
another component within the harness or a slight chafe to grounds preventing a fuse
to open.
Correction
• If less than infinite, repair the short to ground on the circuit.
• If infinite resistance, replace the T19 Power Supply Transformer.
Parts Information
Causal
Part
Description
Part
Number
Qty
X
CONVERTER, M/
FUNC PWR SPLY
13510484
1
Warranty Information
For vehicles repaired under the Bumper-to-Bumper
coverage (Canada Base Warranty coverage), use the
following labor operation. Reference the Applicable
Warranties section of Investigate Vehicle History (IVH)
for coverage information.
Labor
Operation
Description
Labor Time
5080318*
Inspect For Mis-Configured
DC/DC Converter
1.0 hr
*This is a unique Labor Operation for bulletin use only.
Version
1
Modified
Released June 21, 2021
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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