21NA077 Service Bulletin/Repair Instructions

Service Bulletin
Bulletin No.:
21-NA-077
Date:
April, 2021
INFORMATION

Subject:

Brand:
Information on Aero Shutter Related Diagnostic Codes

Model:
Model Year:

from
to
2019
2019
VIN:

from
Engine:
Transmission:
All
All
to
Silverado 1500

(New Model)

Silverado 1500

(New Model - 12th

VIN Digit = 7) - 4WD

Chevrolet
Silverado 1500

Silverado

2500HD/3500HD

Suburban

Tahoe Models
Involved Region or Country
2020

2021
SOP
June

30, 2021
2019
North America, Europe, Middle East
Additional Options (RPOs)

Condition
Some customers may comment on seeing a Check engine lamp illuminated in the DIC.
Cause
The cause of the condition may be a various combination of Aero shutter related

diagnostic codes.
Correction
Check Aero shutter operation, electrical integrity, displaced vanes, and for debris that

could potentially cause the shutter movement to be blocked, following the Service

Information below.
Service Information

Silverado 1500 (New Model) and Silverado 1500

U0284 / U0285

If these codes are paired with any of U0632 / U0633,

U01B0 and U1345, please do the following:

1. Check the fuse for the Aero shutters to ensure that

it is not loose.

2. Check the continuity on the engine wiring harness

to see if there are any high resistances present

along the wiring. If any corrosion is found, repair

the harness. (And report where the failure occurred

with photos).

3. Check the integrity of the J170 splice. Moving this

splice, even small amounts, can cause intermittent

communication issues. If any issues are detected

in the splice, repair the splice and report what was

repaired.
Copyright 2021 General Motors LLC. All Rights Reserved.
4. Check the engagement of the jumper harness to

the shutter actuators. Ensure there is no soft

connection.

5. Check the continuity jumper harness for the Aero

shutters to see if there are any high resistances

present along the wiring. If any corrosion is found,

replace the Aero shutter, not the wiring.

6. Perform a functionality check on the shutters. If

they do work, then do not replace the assemblies,

if they were not replaced at step # 5.

7. Check the X133 connector for corrosion and water

intrusion. Additionally, check the other connectors

to the Aero shutter.

8. If there are signs of water, but not corrosion, please

check the seal condition of the connectors. If they

are not damaged, please apply dielectric grease to

the connector. If there's corrosion present, proceed

to replace the shutter.
Page 2
April, 2021
P059F / P05AE

Please do the following:

Note: For vehicles equipped with upper and lower

shutters, the upper shutter, top passenger side louvre/

vane is intentionally missing from the shutter assembly

for airflow reasons. DO NOT replace the shutter for this

reason.

1. Check for any debris in the upper and lower

shutters. If found, please remove the debris.

2. If there is no debris evident, please look for a

louvre/vane that is disengaged from the linkage. If

the vehicle has a shutter with this condition, please

engage the louvre/vane in the shutter assembly. If

shutter is operational, DO NOT replace the shutter.

3. Check to see if the upper shutter in open position is

binding on the air induction plenum. It is located on

the driver's side upper behind the upper shutter. If

this condition exists, secure the air induction

plenum to structure behind, using a 2–stage

push pin.

Silverado 2500HD/3500HD

P059F- Upper Shutter

Please do the following:

Note: For MY 2020-2021 vehicles equipped with upper

and lower shutters, the upper shutter, top passenger

side louvre/vane is intentionally missing from the

shutter assembly for airflow reasons. DO NOT replace

the shutter for this reason.

1. Before removing the fascia of the vehicle, check for

any debris in upper shutter. Also, utilizing a mirror,

look behind the lower shutter to determine if there

is any debris lodged in the back side.

2. If debris is present, clear the debris from the

assembly by hand or compressed air. If

unsuccessful, remove the shutter from the vehicle

and clear debris, then reinstall the shutter.

3. If there is no debris, please look for a louvre/vane

that is disengaged from the linkage. If the vehicle

has a shutter with this condition, please engage

the louvre/vane in the shutter assembly. DO NOT

replace the shutter.

4. Functionality test the shutter. If they are functional,

DO NOT replace the assemblies.

P05AE - Lower Shutter

Please do the following:

1. Remove the lower shutter from the vehicle and

clear the debris if present from the assembly by

hand or compressed air.

2. For 2020-2021 vehicles only, remove the fourth

lowest row of louvers by completing the Lower

Shutter Louver Modification found in Bulletin

#21-NA-071. If the fourth lowest row is already

missing, move to step #3.

3. Check to see if there is any debris sitting in the

baffle area behind the lower shutter and clear

debris if present.
Bulletin No.: 21-NA-077
4. If there is no debris, please look for a louvre/vane

that is disengaged from the linkage. If the vehicle

has a shutter with this condition, please engage

the louvre/vane in the shutter assembly. DO NOT

replace the shutter.

5. Functionally test the shutters. If they are functional,

DO NOT replace the assemblies

6. If the lower shutter is ordered for replacement

and arrives with all 4 rows of louvers, complete

the Lower Shutter Louver Modification found in

Bulletin #21-NA-071.

U0284 / U0285

Please do the following:

1. Check the fuse for the Aero shutter, to ensure it is

not loose.

2. Check the engine wiring harness to see if there is

any high resistance present along the wiring to the

shutters. If any corrosion/damage is found, the

repair the harness. Report where the failure

occurred with photos or a detailed description.

3. Check the engagement of the jumper harness to

the shutter actuators. Ensure no soft connection.

4. Check the continuity in-jumper harness for the

Aero shutters, to see if there is any high resistance

present along the wiring. If any corrosion is found,

replace the Aero shutter, not the wiring.

5. Perform a functionality check on the shutters. If

they do work, then DO NOT replace the

assemblies, if they were not replaced at step # 4

6. Check the X133 connector for corrosion and water

intrusion. Additionally, check the other connectors

to the Aero shutter.

7. If there are signs of water, but not corrosion, please

check the seal condition of the connectors. If they

are not damaged, please apply dielectric grease to

the connector. If there's corrosion present, proceed

to replace the shutter.

SUV

U0284 / U0285

Please do the following:

1. Check the fuse for the Aero shutters to ensure that

it is not loose.

2. Check the continuity on the engine wiring harness

to see if there are any high resistances present

along the wiring. If any corrosion is found, repair

the harness. (And report where the failure occurred

with photos).

3. Check the engagement of the jumper harness to

the shutter actuators. Ensure there is no soft

connection.

4. Check the continuity jumper harness for the Aero

shutters to see if there are any high resistances

present along the wiring. If any corrosion found,

replace the Aero shutter not the wiring.

5. Perform a functionality check on the shutters if they

do work, then do not replace the assemblies, if

they were not replaced at step # 4
Bulletin No.: 21-NA-077
April, 2021
Page 3
6. Check the X133 connector for corrosion and water

intrusion. Additionally, check the other connectors

to the Aero shutter.

7. If there are signs of water, but not corrosion, please

check the seal condition of the connectors. If they

are not damaged, please apply dielectric grease to

the connector. If there's corrosion present, proceed

to replace the shutter.

P059F / P05AE

Please do the following:

Note: For vehicles equipped with upper and lower

shutters, the upper shutter, top passenger side louvre/

vane is intentionally missing from the shutter assembly

for airflow reasons. DO NOT replace the shutter for this

reason.

1. Check for any debris in the upper and lower

shutters. If found, please remove the debris.

2. If there is no debris, please look for a louvre/vane

that is disengaged from the linkage. If the vehicle

has a shutter with this condition, please engage

the louvre/vane in the shutter assembly. DO NOT

replace the shutter.

3. Check to see if the upper shutter is binding on the

HORN BRACKET. It is located on the passenger’s

side upper, behind the upper shutter.

4. Functionally test the shutters, if they work do not

replace the assemblies.
Parts Information

Use the VIN and refer to the GM Electronic Parts

Catalog (EPC) to determine the proper part to order.
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.

For vehicles repaired under warranty, use the

appropriate labor operation for the repair performed.

Labor Operation
Description
Labor Time
1481528*
Check Aero Shutter Operation and Function
0.8 hr
Add
Complete Lower Shutter Louver Modification
0.2 hr
*This is a unique Labor Operation for Bulletin use only.
Version
1
Modified
Released March 26, 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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