Pop Noise Heard Coming from Rear Roof of Cab Area – 2019-2020 Chevrolet Silverado & GMC Sierra

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Copyright 2021 General Motors LLC. All Rights Reserved.
Service Bulletin Bulletin No.: 21-NA-018
Date: February, 2021
TECHNICAL
Subject: Pop Noise Heard Coming from Rear Roof of Cab Area
Brand: Model:
Model Year: Date Breakpoint: Engine: Transmission:
from to from to
Chevrolet
Silverado 1500
(New Model)
2019 2019
SOP
Prior to
August
3, 2020
All All
Silverado 1500
(New Model – 12th
VIN Digit = 7) – 4WD
Silverado 1500
Silverado 2020 2020
2500HD/3500HD
GMC
Sierra 1500
(New Model) 2019 2019
Sierra 1500
Sierra 2020 2020
2500HD/3500HD
Involved Region or Country North America, Saudi Arabia, Israel, Chile, Peru
Additional Options (RPOs)
Condition
Some customers may comment on hearing a pop noise coming from rear roof of cab
area. The sound may even be described like a rock, or other object, striking the cab.
The sound is also more commonly heard when the cab body is heated, or cooled, by
changes in ambient conditions.
Cause
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Page 2 February, 2021 Bulletin No.: 21-NA-018
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Note: In the graphic examples above, a gap (1) can be noted on the passenger side
lower corner of CHMSL. In the second example a slight wear mark (2) in the spoiler paint
can be seen.
The cause of the condition may be an Interference between the Center High Mount Stop
Lamp (CHMSL) and the body of the spoiler. As these parts expand and contract, with the
changes in ambient conditions, there is a stick-slip condition that generates noise.
Correction Following the steps in the Service Procedure below, apply foam tape between the
CHMSL and the spoiler body, to create space between the CHMSL and spoiler.
Bulletin No.: 21-NA-018 February, 2021 Page 3
Service Procedure
5034888
Important: Discard the 8 original central roof spoiler
nuts, they are NOT reusable fasteners.
1. Remove the roof rear spoiler from the vehicle, and
the CHMSL (2) from the spoiler. Refer to High
Mount Stop Lamp Replacement, in SI,
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2. Cut an approximate 45 mm. (1.75 in.) length of
*Kent Automotive Adhesive-Back Shim Stock P/N
P40100, or equivalent. Then cut that piece in half,
lengthwise.
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3. Apply 1 piece of tape, to each side of the lower
corners of the spoiler, in these areas shown by the
arrows in the graphic above.
Page 4 February, 2021 Bulletin No.: 21-NA-018
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Important: The 8 central roof spoiler nuts are NOT
reusable fasteners. The original fasteners must be
discarded and replaced.
4. Reinstall the CHMSL, and the roof rear spoiler.
Refer to High Mount Stop Lamp Replacement,
in SI,
5. Verify the noise condition has been eliminated.
* We believe this source and their products to be
reliable. There may be additional manufacturers of
such products/materials. General Motors does not
endorse, indicate any preference for, or assume any
responsibility for the products or material from this firm
or for any such items that may be available from other
sources.
Parts Information
Contact Kent Automotive at 1-888-YES-KENTor online
at www.kent-automotive.com.
Causal
Part Description Part
Number
Material
Allowance
or Quantity
N/A
Kent Automotive
Adhesive-Back
Shim Stock
1/8 x 5/8″ x 50′
P40100
42 cents
(U.S.)
63 cents
(Canada)
NUT W/ WASHER
AND SEAL 11611049 8
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
1086308* Remove and Reinstall High Mount Stop Lamp, Add Foam Shim
Stock
1.9 hr.
*This is a unique Labor Operation for Bulletin use only.
Version 1
Modified Released January 27, 2021

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