- High engine idle speed – Compare engine idle
speed to desired idle speed.
-

Bulletin No.: 20-NA-136

A default condition caused by certain DTCs that
result in maximum line pressure to prevent clutch
slippage.

6.2.

Place the gear selector in the DRIVE
position.

6.3.

Accelerate the vehicle using a steady
throttle position between 15 and 20 percent.
Hold the throttle steady.

6.4.

As the transmission upshifts, there should
be a noticeable shift feel or engine speed
change within 1 to 2 seconds of the
commanded gear change. The PC solenoid
pressure command should change to “YES”
for the oncoming clutch and the PC solenoid
pressure command should change to “NO”
for the off going clutch.

6.5.

Note any harsh, soft, or delayed shifts or
slipping. Note any noise or vibration.

6.6.

The torque converter clutch (TCC) feel may
not be noticeable. In many applications the
TCC will apply after the 1-2 shift and TCC
events will not be easily detected using
engine speed. Monitor TCC PC solenoid
pressure command while driving and check
TCC slip speed when the pressure
command indicates that the TCC is
commanded to apply.

6.7.

When the TCC applies, slip speed should be
controlled to below 100 RPM when the
transmission is not shifting, and the throttle

Incomplete adapting or incorrect adapting –
Repeat maneuver multiple times to see if shift
quality improves. If it does not and no DTCs were
set, 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 the delay
improves. If it does not and no DTCs were set,
refer to SI document “Harsh Garage Shift”.
6. Check Upshifts – The TCM calculates the upshift
points based primarily on 2 inputs: throttle position

Bulletin No.: 20-NA-136

May, 2024

is held steady. If the TCC slip exceeds this
value for more than 6 seconds after the TCC
PC Sol. Pressure Command indicates that
the TCC is commanded on:
⇒

Check for DTCs.

⇒

Refer to Torque Converter Diagnosis in SI.

Note: This transmission is equipped with an
electronically controlled capacity clutch (ECCC),
which allows operation of the clutch without fully
locking to the torque converter cover. The clutch
maintains a small amount of slippage, approximately 20 RPM, in 2nd, 3rd, 4th, 5th, and 6th gears,
depending on the vehicle application. ECCC was
developed to reduce the possibility of noise,
vibration or chuggle caused by TCC apply. Full
lockup is available at highway speeds on some
applications.
7. Part Throttle Step-in Downshifts:
7.1.

Place the gear selector in the DRIVE
position.

7.2.

Accelerate the vehicle at light throttle (5-10
percent) until 3rd gear is just achieved.

7.3.

Quickly increase throttle angle until
commanded gear indicates that a downshift
to 2nd gear is commanded.

7.4.

Verify that the transmission downshifts within
2 seconds of the throttle movement.

7.5.

Repeat steps 2 to 4 at higher speed to
achieve 4th gear and then step in to
command a 4th gear to 3rd gear downshift.

7.6.

Repeat steps 2 to 4 at higher speed to
achieve 5th gear and then step in to
command a 5th to 4th gear downshift.

7.7.

Repeat steps 2 to 4 at higher speed to
achieve 6th gear and then step in to
command a 6th gear to 5th gear downshift.

7.8.

Note any harsh, soft, or delayed shifts or
slipping. Note any noise or vibration.
8. Coasting Downshifts:
8.1.

Place the gear selector in the DRIVE
position.

8.2.

Accelerate the vehicle to 6th gear with the
TCC applied.

8.3.

Release the throttle and apply the brakes.

8.4.

Verify that the downshifts occur as
commanded by monitoring gear ratio, which
should change after commanded gear
changes.

8.5.

Note any harsh, soft, or delayed shifts or
slipping. Note any noise or vibration.
9. Reverse:
9.1.

With the vehicle stopped, move the gear
selector to REVERSE.

Page 5
9.2.

Slowly accelerate the vehicle to a 10-15
percent throttle position.

9.3.

Verify that there is no noticeable slip, noise,
or vibration.
10. Road Test Results:
10.1. Diagnostic TIP: If completion of the above
tests are inconclusive to isolate if the transmission shifting concern(s) are internal
transmission or input/command, can use the
control function feature in GDS2 to
command all shifts. If when using GDS2 to
command shifts and transmission shifts into
each range commanded, the concern is
generally an input/command concern, and
not an internal transmission concern. If
ranges are not completed when using GDS2
to command, then generally the concern is
an internal transmission concern and not an
input/command concern.
10.2. If noise or vibration concern is noted, follow
Noise and Vibration Analysis in SI using
Chassis Ears and PICO scope in diagnosis.
10.3. If upshifts and downshifts are harsh, soft,
delayed, or slip, follow SI diagnosis for
condition.
Step Five — DTC
If any of the following DTCs are Current or reset during
the road test, record on the repair order and follow the
instructions below for that DTC.
• P0796 Transmission Control Solenoid Valve 3
Stuck Off
• P0797 Transmission Control Solenoid Valve 3
Stuck On
• P2723 Transmission Control Solenoid Valve 5
Stuck Off
• P2724 Transmission Control Solenoid Valve 5
Stuck On
If any of the above first group of DTCs are current or
reset on the road test the transmission must be
removed from the vehicle and inspected for damage to
the clutch plates. If hot spots or other evidence of a
slipping clutch, then follow SI procedure for
replacement of the affected clutch plates and replace
both the solenoid body and valve body.
• P0746 Transmission Control Solenoid Valve 1
Stuck Off
• P0747 Transmission Control Solenoid Valve 1
Stuck On
• P2731 Transmission Control Solenoid Valve 6
Performance
• P2732 Transmission Control Solenoid Valve 6
Stuck Off

Page 6

May, 2024

• P2733 Transmission Control Solenoid Valve 6
Stuck On
• P2820 Transmission Control Solenoid Valve 9
Stuck Off
• P2821 Transmission Control Solenoid Valve 9
Stuck On
• P187D Transmission Park Valve Stuck On
• P18AA Transmission Range Control Valve 1
Position Switch Circuit Stuck On
• P18AB Transmission Range Control Valve 1
Position Switch Circuit Stuck Off
• P18AC Transmission Range Control Valve 2
Position Switch Circuit Stuck On
• P18AD Transmission Range Control Valve 2
Position Switch Circuit Stuck Off
• P18AE Transmission Range Control Enable Valve
Stuck Off
If any of the above second group of DTCs are current
or reset on the road test and the transmission fluid is
red, translucent, and doesn’t have a burnt odor, then
only replace both the solenoid body and valve body. If
the transmission fluid is very dark or black, not translucent, and has a burnt odor, then in addition to
replacing the solenoid body and valve body, the transmission should be removed from the vehicle and
inspected for damage to the clutch plates, if found
follow SI procedure to replace them.
• P0741 Torque Converter Clutch (TCC) System
Stuck Off
• P0776 Transmission Control Solenoid Valve 2
Stuck Off
• P0777 Transmission Control Solenoid Valve 2
Stuck On
• P2817 Transmission Control Solenoid Valve 8
Stuck Off
• P2818 Transmission Control Solenoid Valve 8
Stuck On
If any of the above third group of DTCs are current or
reset on the road test and the transmission fluid is red,
translucent, and doesn’t have a burnt odor, then only
replace the solenoid body. If the transmission fluid is
very dark or black, not translucent, and has a burnt
odor, then in addition to replacing the solenoid body,
the transmission should be removed from the vehicle
and inspected for damage to the clutch plates, if found
follow SI procedure to replace them.
• P2714 Transmission Control Solenoid Valve 4
Stuck Off
• P2715 Transmission Control Solenoid Valve 4
Stuck On
• P187D Transmission Park Valve Stuck On
• P187E Transmission Park Valve Stuck Off

Bulletin No.: 20-NA-136

If any of the above fourth group of DTCs are current or
reset on the road test and the transmission fluid is red,
translucent, and doesn’t have a burnt odor, then only
replace the valve body. If the transmission fluid is very
dark or black, not translucent, and has a burnt odor,
then in addition to replacing the valve body, the transmission should be removed from the vehicle and
inspected for damage to the clutch plates. If found,
follow SI procedure to replace them.
• P0721 Output Speed Sensor Performance
• P0722 Output Speed Sensor Circuit No Signal
• P0723 Output Speed Sensor Circuit Intermittent
If any of the above fifth group of DTCs are current or
reset on the road test and the transmission fluid is red,
translucent, and doesn’t have a burnt odor, then follow
SI diagnostic for the output speed sensor.
• P18A8 Transmission Park Control Solenoid
Actuator Stuck Off
• P18E7 Transmission Park Valve Position Sensor 1
Performance
• P18E8 Transmission Park Valve Position Sensor 2
Performance
• P27EC Transmission Range Control Valve 1
Position Switch Performance
• P27F0 Transmission Range Control Valve 2
Position Switch Performance
Note: If P18A8 is set then also replace the Park inhibit
Solenoid Actuator along with the solenoid body and
valve body.
If any of the above sixth group of DTCs are current or
reset on the road test and the transmission fluid is red,
translucent, and doesn’t have a burnt odor, then check
vehicle battery health and state of charge per SI
instructions, also check battery, TCM, and Transmission ground for voltage loss. If battery and grounds
do not show problem and DTC is current, then replace
both the solenoid body and valve body. If the transmission fluid is very dark or black, not translucent, and
has a burnt odor, then in addition to replacing the
solenoid body and valve body, the transmission should
be removed from the vehicle and inspected for damage
to the clutch plates. If found, follow SI procedure to
replace them.
If any of the DTCs are not reproduced during testing
and only seen in History, then perform the Transmission
Service Fast Learn Procedure. If no DTCs, reset and
return the vehicle to the customer.
Symptoms other than listed above should be diagnosed
using SI procedures and repaired as necessary.

Bulletin No.: 20-NA-136

May, 2024

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

Page 7

Note: If transmission is removed from vehicle and internally inspected for clutch or hardware failure, use
appropriate control valve body or control solenoid body
labor operation for the DTC and include the clutch or
hardware inspection and repair time as straight time to
the labor operation.

Note: EMISSION WARRANTY COVERAGE CODE E,
E1 APPLIES TO LABOR OPERATION 846369.
Labor Operation

Description

Labor Time

8481048*

Perform Fluid Level and Oil
Pressure Checks and
Service Fast Learn

1.5 hrs

8463690***

Control Valve Body
Replacement

8463700

Control Valve Solenoid
Body Replacement

Use Published Labor
Operation
Time

*This is a unique Labor Operation for bulletin use only.
This operation is only used if transmission assembly is not
replaced.
**Because the transmission is not to be disassembled for
this bulletin, the 1.5 hours add time for “Disassemble,
Inspect, Determine Repair and Re-assemble for Core
Return” should not be claimed.
***If valve body and solenoid body are replaced at the
same time use this labor operation.
Version

13

Modified

Released June 26, 2020
Revised August 18, 2020 – Added the Warranty Information section.
Revised September 25, 2020 – Added the 2021 Model Year.
Revised May 26, 2021 - Update information in the Overview section, Step One-DTC section, Step Five DTC section and the Warranty Information section.
Revised July 13, 2021 - Update information in the Overview section after Step 3 to
Extend Pilot Program.
Revised August 05, 2021 - Added the 2022 Model Year.
Revised October 01,2021 - Add Attention statement, Update Overview and Warranty
Information section.
Revised November 23, 2021 – Updated #5 under Overview.
Revised February 17, 2021 - Removed PIP5697B and Added 21–NA-201 in the Overview section.
Revised July 20, 2022 - Remove P187E, P18E7 and P18E8 from the Step 5 - DTC section.
Revised August 04, 2022 - Removed 2018 and 2019 from Model Year and Added 2023 to
Model Year.
Revised August 02, 2023 - Removed 2020 from Model Year and Added 2024 to Model
Year.
Revised May 03, 2024 - Added PIP5974 under Overview section.

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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