Bulletin No.:

Service Bulletin

Date:

21-NA-293
August, 2023

TECHNICAL
Subject:

Poor Engine Performance in Extremely Cold Weather Conditions, Charge Air Cooler
Icing - Malfunction Indicator Lamp (MIL) Illuminated, DTC P0299, P0234, P0236,
P00C7 Set
Model Year:

Brand:

Model:

Buick

Encore GX

2020

Chevrolet

Trailblazer

2021

Involved Region or Country

from

to

VIN:
from

Engine:

Transmission:

to

2023

United States and Canada

Additional Options (RPOs)

Condition

Some customers may comment that when driving short distances and/or slow speed
driving cycles, within the first 10 to 15 minutes of vehicle operation in extremely cold
weather conditions (-18°C or less / 0°F or less) vehicle may experience several
conditions. After driving for a period of time, the drivability issues seem to diminish.
Vehicles may experience one or several of the following conditions:
• Loss of power
• Hesitation on acceleration
• Possible Malfunction Indicator Lamp illuminated
Technicians may also find one or more of the following DTCs:
• P0234
• P0236
• P0299
• P00C7
Note: This condition may also cause an increase in crankcase pressure, creating oil
leaks at seals and gaskets.

Cause

The cause of the condition may be ice accumulation in the charge air cooler (CAC),
restricting air flow to the throttle body.

Correction

Reprogram the Engine Control Module.
Note: See 20-NA-028 for adding a winter cover for vehicles in Canada

Customer Information

Copyright 2023 General Motors LLC. All Rights Reserved.

The customer must be informed by dealership personnel by explaining the new engine
control module calibration and its effects on transmission shift patterns at highway
speeds during cold weather to avoid a customer return to the dealership after the
programming is completed. Follow published diagnostics for each DTC.
The new calibration will enable a revised transmission shift pattern during cold weather
operation which does not use overdrive as frequently. As a result, some customers may
notice elevated engine RPM’s during highway operation. This operating mode will reduce
the potential for ice to build up inside the charge air cooler, and the potential for setting
P0299 or P0234 diagnostic codes.

Page 2

August, 2023

Service Procedure
Important: Service agents must comply with all
International, Federal, State, Provincial, and/or
Local laws applicable to the activities it performs
under this bulletin, including but not limited to
handling, deploying, preparing, classifying,
packaging, marking, labeling, and shipping
dangerous goods. In the event of a conflict between
the procedures set forth in this bulletin and the
laws that apply to your dealership, you must follow
those applicable laws.
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.
• 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
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
• Clear DTCs after programming is complete.
Clearing powertrain DTCs will set the Inspection/
Maintenance (I/M) system status indicators to NO.

Bulletin No.: 21-NA-293

Important: The service technician always needs to
verify that the VIN displayed in the TLC left side drop
down menu and the top center window match the VIN
plate of the vehicle to be programmed prior to using
Service Programming System 2 (SPS2) for
programming or reprogramming a module.
• For the TLC application, service technicians need
to always ensure that the power mode (ignition) is
“ON” before reading the VIN from the vehicle’s
VIN master module and that they do not select a
VIN that is already in the TLC application memory
from a previous vehicle.
• If the VIN that shows up in the TLC top center
window after correctly reading the VIN from the
vehicle does not match the VIN plate of the
vehicle, manually type in the VIN characters from
the vehicle VIN plate into the TLC top center
window and use these for programming or
reprogramming the subject module with the
correct vehicle VIN and software and/or
calibrations.
• The Engine Control Module (ECM) is the master
module (for VIP vehicles) that TLC reads to
determine the VIN of the vehicle. If the VIN read
from the vehicle by TLC does not match the VIN
plate of the vehicle, the ECM also needs to be
reprogrammed with the correct VIN, software and
calibrations that match the vehicle’s VIN plate.
• The Body Control Module (BCM) is the master
module (for GEM vehicles) that TLC reads to
determine the VIN of the vehicle. If the VIN read
from the vehicle by TLC does not match the VIN
plate of the vehicle, the BCM also needs to be
reprogrammed with the correct VIN, software and
calibrations that match the vehicle’s VIN plate.

Bulletin No.: 21-NA-293

August, 2023

Page 3

Caution: Be sure the VIN selected in the drop down
menu (1) is the same as the vehicle connected (2)
before beginning programming.

5743643

Important: If the vehicle VIN DOES NOT match, the
message below will be shown

5877000

Page 4

August, 2023

Bulletin No.: 21-NA-293

5644477

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.
1. Reprogram the Engine Control Module. Refer to
K20 Engine Control Module: Programming and
Setup in SI.

Bulletin No.: 21-NA-293

August, 2023

Page 5

Note: Select this calibration ONLY to address issues
related to charge air cooler icing occurring on vehicles
operated in cold climates.

5644478

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.

Page 6

August, 2023

Bulletin No.: 21-NA-293

Warranty Information
Warranty coverage code E2 applies for this module
programming event. ECM reprogramming is covered
for 8 years/80,000 miles (U.S.) or 8 years/130,000 km
(Canada).
Labor Operation

Description

Labor Time

*2888338

Engine Control Module Reprogramming with SPS for Cold
Weather Engine Performance

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:

6125814

•
•

The Warranty Claim Code must be accurately entered in the “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 “Warranty Claim Code”
field of the transaction, otherwise the transaction will reject. It is best practice to enter the FINAL code provided by SPS2.
Note: Select this calibration ONLY to address issues related to charge air cooler icing occurring on vehicles operated in cold
climates.

Bulletin No.: 21-NA-293

August, 2023

Page 7

Warranty Claim Code Information Retrieval

6125774

If the Warranty Claim Code was not recorded on the
Job Card, the code can be retrieved in the SPS2
system as follows:
1. Open TLC on the computer used to program the
vehicle.
2. Select and start SPS2.
3. Select Settings (1).
4. Select the Warranty Claim Code tab (2).
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

3

Modified

Released January 10, 2022
Revised January 13, 2022 – Added note to Correction Section and updated warranty
statement in Warranty Information.
Revised July 28, 2023 – Added 2023 Model Year and updated Programming Procedure.

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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