Bulletin No.:

Service Bulletin

Date:

18-NA-035
February, 2020

INFORMATION
Subject:

Brand:

Buick

Information on Transmission No Command Overdrive Ranges During Cold Ambient
Temperatures

Model:

Model Year:

Encore

2018

2019

1.4L (LE2)

6T40 (MNH)

Encore
(VIN J)

2020

2020

1.4L (LUV)

6T40 (MNH)

2019

1.4L (LE2)

6T35 (MNU)

1.5L (LYX)

6T40 (MNH)

1.5L (LFV)

6T40 (MNH)

1.5L (LYX)

9T45 (M3U)

2018

Malibu
GMC

to

Transmission:
(Automatic)

to

Equinox

from

Engine:

from

Cruze (Gen
II - B)
Chevrolet

VIN:

2020

Terrain

Involved Region or Country

North America, Middle East, South Korea, Africa, Israel, Brazil, Colombia, Ecuador, Chile,
Uruguay, Peru

Condition

Some customers may comment that the transmission will not shift into overdrive range
during cold ambient temperatures.
This condition may be caused by the engine control system detecting conditions that
indicate the freezing of moisture in the charge air cooler.
Note: Diagnostic aid overdrives ranges can only be commanded with GDS tool to
confirm correct transmission operation.

Information

When the control system detects the above conditions and the ambient temperature is
either below 0°C (32°F) or slightly above 0°C (32°F) with high moisture, but not frozen, it
takes the following actions:
• Requests a lower gear than normal (resulting in higher RPM).
• The system will enable the condition as needed to prevent freezing.

⇒ This strategy is to prevent a potential excessive air restriction due to an icing
condition, which would lead to a P0299 DTC and reduced engine
power mode.
Explain to the customer their vehicle is operating normally. Do not attempt to repair or
replace any parts to alter the original vehicle design intent. You may wish to give the
customer a copy of this bulletin.

Version

4

Modified

Released February 2, 2018
February 12, 2018 – Updated the temperature readings to 0°C (32°F) and removed a
transmission for the Terrain.
February 21, 2019 – Removed M3U from Equinox, revised the Subject title, added a Note
and temperature slightly above 0°C (32°F) to the Information section.
February 3, 2020 – Added the 2020 Model Year.

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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