21NA149 Service Bulletin/Repair Instructions

Subject: Engine Wire Harness Chafing
Brand:
Model:
Model

Year:

from
Chevrolet
to
VIN:
Engine:
Transmission:
from ot
Silverado 1500 (New Mod2019 2019

el)

Silverado 1500
2020 2021
Sierra 1500 (New Model)
2019 2019
Sierra 1500
2020 2021
Equipped with L82, L84, L87, LV3, L3B, or LM2
GMC
Involved

Region United States, Canada, Mexico, Middle East, Chile, Paraguay, Uruguay, Thailand, Australia and New Zealand.

or

Country

Additional

Options

(RPOs)

Some customers may comment on one or more of the following conditions:

• Check Engine light illuminated

• Reduced Engine Power (REP)

Condi• Reduced Power Steering Assist

tion

• Transmission erratically shifting

• No start condition

• Vehicle stalls
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Example of extreme wire chaffing

The cause of the condition may be an engine wire harness clip was removed during production due to ergonomic issues (hand

Cause clearance and branch stiffness). This led to an uncontrolled branch that came into contact with the ECM/TCM bracket, driver side

upper control arm, and/or shock tower and caused chaffing during engine vibration and roll.

Correction
Utilizing Engine Harness sleeves, anti-abrasion tape, and zip-ties to secure the harness away from one or more of the chaffing

points. Follow the Service Procedure steps below.
Service Procedure

1. Lift and support the vehicle. Refer to Lifting and Jacking the Vehicle in SI.

2. Remove driver side tire and wheel and driver wheelhouse liner. Refer to Tire and Wheel Removal and Installation,

and Front Wheelhouse Liner Replacement in SI.
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3. Locate the three contact points where the wire harness is chaffing, the ECM/TCM black bracket (1), the upper control

arm (2), and the shock tower bolt (3).
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4. At the ECM/TCM bracket, locate the wire harness laying against the ledge (1).
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Wrap the wire harness with the shorter Engine Harness Sleeve then utilizing zip ties and two small holes in the

bracket (1).
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Secure the harness snug to the bracket to prevent movement.
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5. At the upper control arm (1), secure the harness away from control arm (example above shows harness in the correct

position, unwrapped).
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Wrap the harness in the shorter Engine Harness Sleeve then wrap with anti-abrasion tape secure it to the harness

clip above the ECM/TCM bracket (1) to keep out of the way of the upper control arm.
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6. At the shock tower point there is a wire harness canal (1).
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Using the long Engine Harness Sleeve, wrap the harness and secure it snug to the canal using zip-ties.
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7. Verify the wire harness is wrapped and secured at all three points, the ECM/TCM Bracket (1), Upper Control Arm

(2), and the Shock Tower (3). Then reassemble the vehicle.

8. Reinstall the front wheelhouse liner and tire and wheel. Refer to Front Wheelhouse Liner Replacement and Tire and

Wheel Removal and Installation in SI.

9. Remove the support and lower the vehicle.
Parts Information

Causal

Part
Description
Part Number
X
Engine Harness Sleeve
84820678
X
Engine Harness Sleeve
84826758
X
Tie Strap
12337820
Qy

t
Causal

Part
Description
Part Number
X
Black Push Pin Tie

Strap
84396606
Qy

t
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
*5486188
Wrap and Secure Engine Wire Harness
1.3 hr
*This is a unique Labor Operation for Bulletin use only.
Version
1
Modified
Released June 29,

2021

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