Service Bulletin

Bulletin No.:

21-NA-096

Date:

May, 2021

TECHNICAL
Subject:

Cooling Fans Continuously Run, Malfunction Indicator Lamp (MIL) Illuminated - DTC
P2B60, P1098, P26BB, P149D, P0421, and/or P0606 Set

Brand:

Model:

Chevrolet

Silverado 1500

GMC

Sierra 1500

Model Year:

Breakpoint Date:

from

to

from

to

2021

2021

SOP

April
28, 2021

Engine:

Transmission:

LM2

Involved Region or Country

North America

Condition

Some customers may comment on one or more of the following conditions:
• Mil Illuminated
• Cooling fans continuously run
Some technicians may find one or more of the following codes set in the Engine Control
Module (ECM):
• P0421: Catalytic Convertor Low Efficiency
• P0606: Control Module Processor Performance
• P1098: Engine Coolant Control Valve Position Sensor Minimum Stop Performance
• P149D: Engine Coolant Temperature Sensor 5 Not Plausible
• P2B60: Engine Coolant Flow Control Valve Position Sensor Performance
• P26BB: Engine Coolant Control Valve Performance

Cause

This condition may be caused by a software anomaly.

Correction

If any of the DTCs listed above have set, program the ECM to the latest software
available.

Service Procedure
Caution: Before downloading the update files, be sure
the computer is connected to the internet through a
network cable (hardwired). DO NOT DOWNLOAD or
install the files wirelessly. If there is an interruption
during programming, programming failure or control
module damage may occur.
Note: Carefully read and follow the instructions below.
•

•

Ensure the programming tool is equipped with the
latest software and is securely connected to the
data link connector. If there is an interruption
during programming, programming failure or
control module damage may occur.
Stable battery voltage is critical during
programming. Any fluctuation, spiking, over
voltage or loss of voltage will interrupt
programming. Install a GM Authorized
Programming Support Tool to maintain system

Copyright 2021 General Motors LLC. All Rights Reserved.

voltage. Refer to www.gmdesolutions.com for
further information. If not available, connect a fully
charged 12 V jumper or booster pack
disconnected from the AC voltage supply. DO
NOT connect a battery charger.
• Follow the on-screen prompts regarding ignition
power mode, but ensure that anything that drains
excessive power (exterior lights, HVAC blower
motor, etc) is off.
• Please verify that the radio time and date are set
correctly before inserting USB drive into vehicle
for programming, otherwise an error will result..
• Clear DTCs after programming is complete.
Clearing powertrain DTCs will set the Inspection/
Maintenance (I/M) system status indicators to NO.
Caution: Be sure the VIN selected in the drop down
menu (1) is the same as the vehicle connected (2)
before beginning programming.

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Important: Techline Connect and TIS2WEB screens
shown above.
Important: If the same calibration/software warning is
noted on the TLC or SPS Summary screen, select OK
and follow screen instructions. After a successful
programming event, the WCC is located in the Service
Programming System dialogue box of the SPS
Summary screen. No further action is required. Refer to
the Warranty section of the bulletin.

Important: When programming a module in GM’s new
Vehicle Intelligence Platform, or VIP, the power mode
(ignition) needs to be off or errors may occur. This
involves the 2020 Chevrolet Corvette, Cadillac CT5 and
CT4, as well as the upcoming full-size Chevrolet, GMC,
Cadillac SUVs and Buick Envision. Serial Data
Message Authentication also needs to have the
ignition off.
1. Reprogram the ECM module. Refer to K20 Engine
Control Module: Programming and Setup in SI.
Modify as required.

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Note: The screenshots above are an example of
module programming and may not be indicative of the
specific module that is being programmed. Module
selection and VIN information have been blacked out.
Important: To avoid warranty transaction rejections,
you MUST record the warranty claim code provided on
the SPS Warranty Claim Code (WCC) screen shown
above on the job card. Refer to callout 1 above for the
location of the WCC on the SPS screen
2. Record SPS Warranty Claim Code on job card for
warranty transaction submission.

Parts Information
No parts are required for this repair.

Warranty Information
For vehicles repaired under the Emission coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Labor Operation

Description

Labor Time

2887268*

ECM Reprogramming with SPS for DTC P2B60, P1098,
P26BB, P149D, P0421, and/or P0606

0,3 hr

*This is a unique Labor Operation for Bulletin use only.
Important: **To avoid warranty transaction rejections, carefully read and follow the instructions below:
• The Warranty Claim Code must be accurately entered in the “SPS Warranty Claim Code” field of the transaction.
• When more than one Warranty Claim Code is generated for a programming event, it is required to document all Warranty
Claim Codes in the “Correction” field on the job card. Dealers must also enter one of the codes in the “SPS Warranty Claim
Code” field of the transaction, otherwise the transaction will reject. It is best practice to enter the FINAL code provided by
SPS/SPS2.

Warranty Claim Code Information Retrieval
If the SPS Warranty Claim Code was not recorded on
the Job Card, the code can be retrieved in the SPS
system as follows:
1. Open TLC/TIS on the computer used to program
the vehicle.
2. Select and start SPS/SPS2.
3. Select Settings.
4. Select the Warranty Claim Code tab.
The VIN, Warranty Claim Code and Date/Time will be
listed on a roster of recent programming events. If the
code is retrievable, dealers should resubmit the
transaction making sure to include the code in the SPS
Warranty Claim Code field.

Version

1

Modified

Released May 03, 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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