Bulletin No.:

Service Bulletin

Date:

21-NA-169
August, 2023

TECHNICAL
Subject:

Diagnostic Tip for DTCs Set at a Low Mileage for 9T45/50/60 Automatic Transmissions

Attention: This bulletin only applies to vehicles with less than 19,000 km (12,000 miles) on the
odometer.
Model Year:
Brand:

Buick

Model:

from

Envision

M3T, M3H
2024

M3H

XT5
Blazer

GMC

to

Transmission:
(9T45, 9T50 or 9T60
Automatic)
M3F

XT6
Chevrolet

from

Engine:

Encore GX
XT4

Cadillac

to

VIN:

M3G
2021

2024

—

—

—

M3G
M3D, M3T

Malibu

2023

M3E

Trailblazer

2024

M3F

Acadia
Terrain

Involved Region or Country
Condition

Information

Copyright 2023 General Motors LLC. All Rights Reserved.

2024

M3H, M3G
M3H, M3U

North America, Middle East, Europe
The purpose of this bulletin is to aid the service technician in diagnosing 9T45/50/60
automatic transmissions with low mileage and DTCs current or history related to the
control solenoids and valves. Follow the Service Procedure steps below to determine
repair strategy.
Important: For vehicles equipped with 9T65 transmissions (RPO M3V or M3W), do not
follow this bulletin and refer to Service Bulletin # 20-NA-136.
Please refer to these service publications for resolutions to customer comments prior to
proceeding with this bulletin:

⇒ 21-NA-038: Humming Noise Heard Coming From Front End of Vehicle When
Driving at Highway Speeds (Blazer)
⇒ 19-NA-023: High Pitch Whine Noise Heard at 32-56 km/h (20-35 mph) in Any
Gear Under Light to Moderate Acceleration (Equinox, Terrain)
⇒ 20-NA-165: Flutter or Boom Noise at 1200 RPM- Service Calibration
(Trailblazer, Encore GX)
⇒ 21-NA-122: Vibration or Boom At 1300 RPM (Equinox, Terrain)
⇒ 21-NA-201: Information on DTC P0747 Setting at Engine Shut Down When
Transmission is in Park/Neutral with No Hydraulic/Mechanical Transmission
Concern
⇒ 21-NA-118: Vibration Type Noise Heard at Highway Speeds or with Engine
Speed at 1,300-1,500 RPM (XT5, XT6, Blazer, Acadia)

Page 2

August, 2023

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.

Bulletin No.: 21-NA-169

8. Record fluid level; overfilled, under-filled, correct
on repair order and how much was needed to fill or
came out:
• If fluid is overfilled, set correct level and retest.
• If fluid is under-filled, inspect for external leaks.
Refer to Fluid Leak Diagnosis in SI.

Service Procedure
Step One - DTCs
Check all Modules for DTCs. Records of all DTCs,
Current or History, and Module Located In/On Repair
Order.

Step Two - Fluid Level and Condition Check
Note: Ensure the transmission has enough fluid in it to
safely start the vehicle without damaging the
transmission. With the vehicle off and the transmission
fluid temperature at approximately 20–25°C (68–77°F),
there must be at least enough fluid to drain out of the
fluid level hole. This will ensure that there is enough
fluid in the sump to fill the components once the vehicle
is started.
1. Start the engine.
2. Depress the brake pedal and move the shift lever
through each gear range, pausing for about 3
seconds in each range. Then move the shift lever
back to PARK (P).
3. Allow the engine to idle 500–800 rpm for at least 3
minutes to allow any fluid foaming to dissipate and
the fluid level to stabilize.
4. Release the brake pedal.
5. Keep the engine running and observe the
transmission fluid temperature (TFT) using the
Driver Information Center (DIC) or a scan tool.
Caution: The transmission fluid level must be checked
when the transmission fluid temperature (TFT) is at 85–
95°C (185–203°F). If the TFT is not at this temperature,
operate the vehicle or allow the fluid to cool as
required. Setting the fluid level with a TFT outside this
temperature will result in either an under or over-filled
transmission. TFT 95°C under-filled, TFT 85°C
over-filled. An under-filled transmission will cause
premature component wear or damage. An over-filled
transmission will cause fluid to discharge out the vent
tube, fluid foaming, or pump cavitation.
6. Raise the vehicle on a hoist. The vehicle must be
level, with the engine running and the shift lever in
the PARK range.
7. While the vehicle is idling, remove the oil level set
plug (1). Allow any fluid to drain:
• If the fluid is flowing as a steady stream, wait
until the fluid begins to drip.
• If no fluid comes out, add fluid until fluid
drips out.

5840393

9. If fluid level is correct, then check condition of the
fluid:
• The fluid should be red or brown.
• The fluid should be transparent so that objects
or writing can be seen through it. Sample #1 is
an example of acceptable fluid. Sample #2 is an
example of very dark fluid. Sample #3 is an
example of black fluid.
• In addition to checking the fluid color and
transparency, the fluid should be checked for an
odor of burnt fluid. If the fluid is very dark, black,
or has a burnt odor it would indicate clutch
damage has occurred internally in the
transmission and it would need to be removed
from the vehicle and investigated.
• Fluid that is cloudy or milky or appears to be
contaminated with water indicates engine
coolant or water contamination. Refer to the last
version of Service Bulletin 08-07-30-035 for
testing and, if confirmed, find the source of the
coolant/water and repair. Then follow service
manual instructions “engine coolant/water in
transmission” to repair the transmission.
• Inspect the fluid for excessive metal particles or
other debris:
– A small amount of “friction” material is a
“normal” condition.
– A small amount of “metal” from the
manufacturing process is a “normal”
condition. This is observed as fine silver
streaks floating in the fluid.
– If large pieces and/or metal pieces are noted
in the fluid, or the fluid when rubbed between
fingers feels gritty/sandy, it would indicate

Bulletin No.: 21-NA-169

August, 2023

hardware damage has occurred internally in
the transmission and it would need to be
removed from the vehicle and investigated.
• Inspect for external leaks. Refer to Fluid Leak
Diagnosis in SI.
– If fluid level and condition are OK, proceed to
next step.

Step Three - Line Pressure Check
Warning: Keep the brakes applied at all times in
order to prevent unexpected vehicle motion.
Personal injury may result if the vehicle moves
unexpectedly.
Note: You may need to remove or disconnect
components in order to gain access to the transmission
line pressure test hole plug.
1. Remove the line pressure test hole plug. Refer to
Automatic Transmission Fluid Pressure Test Hole
Plug Replacement in SI.
2. Install the GE-21867 Pressure Gauge.
3. Start the engine.
4. Verify the Transmission Fluid Pressure = Greater
than 345 kPa (50 psi).
• If pressure is below 50 psi, record on the repair
order and follow SI document for Fluid Pressure
High or Low.
• If above 50 psi, proceed to next step.
5. Turn the engine OFF.
6. Remove the GE-21867 Pressure Gauge.
7. Install and tighten line pressure test hole plug.
Refer to Automatic Transmission Fluid Pressure
Test Hole Plug Replacement in SI.

Step Four - Perform Road Test
Perform step 1-4 first in order to ensure the electronic
transmission components are functioning properly. If
these components are not checked, a simple electrical
condition could be misdiagnosed.
1. Connect the scan tool.
2. Ensure the gear selector is in PARK and set the
parking brake.
3. Start the engine.
4. Verify that the following scan tool data can be
obtained and is functioning properly.
⇒ Refer to Control Module References for typical
data values. Data that is questionable may
indicate a concern.
5. Check the garage shifts:
⇒ Apply the brake pedal and ensure the parking
brake is set.
⇒ Move the gear selector through the following
ranges:
• PARK to REVERSE
• REVERSE to NEUTRAL
• NEUTRAL to DRIVE
• DRIVE to REVERSE
• REVERSE to DRIVE
⇒ Pause 2 to 3 seconds in each gear position.

Page 3

⇒ Verify the gear engagements are immediate
(less than 2 seconds to complete if transmission
fluid temperature is above 20°C (68°F) and not
harsh. Note that these shifts may be almost
imperceptible in some applications. Using the
scan tool to monitor Transmission ISS,
achieving 0 rpm can be used to check delay in
these cases.
Note: Harsh engagement may be caused by any of the
following conditions:
• High engine idle speed – Compare engine idle
speed to desired idle speed.
• A default condition caused by certain DTCs that
result in maximum line pressure to prevent
clutch slippage.
• Incomplete adapting or incorrect adapting –
Repeat maneuver multiple times to see if shift
quality improves. If it does not and no DTCs
were set, then refer to SI document “Harsh
Garage Shift”.
Note: Delayed engagement may be caused by any of
the following conditions:
• Low idle speed – Compare engine idle speed to
desired idle speed.
• Low fluid level.
• Cold transmission fluid temperature (TFT) –
Use the scan tool to determine TFT.
• Selector linkage – Inspect and adjust as
necessary.
• Incomplete adapting or incorrect adapting –
Repeat maneuver multiple times to see if delay
improves. If it does not and no DTCs were set,
then refer to SI document “Harsh Garage Shift”.
6. Check Upshifts – The TCM calculates the upshift
points based primarily on 2 inputs: throttle position
and vehicle speed. When the TCM determines that
conditions are met for a shift to occur, the TCM
commands the shift by varying current to the
appropriate PC solenoids to control oncoming and
off going clutch pressures.
⇒ Monitor the following scan tool parameters: